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  • 1.
    Bondesson, Laban
    et al.
    KTH.
    Hugosson, Håkan Wilhelm
    Calculations of the cavitation volumes and partial molar volumes of drugs in waterManuskript (preprint) (Annet vitenskapelig)
  • 2.
    de Almeida, Katia Julia
    et al.
    KTH.
    Rinkevicius, Zilvinas
    KTH.
    Hugosson, Håkan Wilhelm
    KTH.
    Ferreira, Amary Cesar
    Universidade Federal de Minas Gerais, Brazil.
    Ågren, Hans
    KTH.
    Modeling of EPR parameters of copper(II) aqua complexes2007Inngår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 332, nr 2-3, s. 176-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we report density functional theory calculations of the electronic g-tensor and hyperfine coupling constants of the copper dication in sixfold- and fivefold-coordination models of the first aqueous solvation sphere. The obtained results indicate that the electronic g-tensor of these copper complexes in combination with hyperfine coupling constants of copper in principle can be used to elucidate the coordination environment of the hydrated copper dication. In addition to these results, we have designed a methodology for accurate evaluation of electronic g-tensors and hyperfine coupling tensors in copper complexes, and demonstrate the applicability of this approach to copper dication aqua complexes.

  • 3.
    de Almeida, Katia Júlia
    et al.
    KTH.
    Murugan, N. Arul
    KTH.
    Rinkevicius, Zilvinas
    KTH.
    Hugosson, Håkan Wilhelm
    KTH.
    Vahtras, Olav
    KTH.
    Ågren, Hans
    KTH.
    Cesar, Amary
    Universidade Federal de Minas Gerais.
    Conformations, structural transitions and visible near-infrared absorption spectra of four-, five- and six-coordinated Cu(ii) aqua complexes2009Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, nr 3, s. 508-519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have performed Car–Parrinello molecular dynamics simulations at ambient conditions for four-, five- and six-coordinated Cu(II) aqua complexes. The molecular geometry has been investigated in terms of Cu–O, Cu–H bond lengths and O–Cu–O bond angles and compared with earlier experimental measurement results and theoretical calculations. We find that the average Cu–O and Cu–H bond lengths increase with increasing coordination number. We have also observed relatively faster structural transition in the case of five-coordinated complex between trigonal bipyramidal and square pyramidal geometry. This result deviates from the findings of the earlier report (A. Pasquarello et al., Science, 2001, 291, 856) on copper(II) in aqueous solution and we attribute these differences to the neglect of solvent environment in our calculations. The averaged absorption spectra for the copper(II) aqua complexes have been computed using spin-restricted density functional linear response formalism taking 100 snap shots from a trajectory of 0.48 ps. We find that the calculated spectra are significantly different, showing clear features that distinguish each coordination model. Comparison with the experimentally reported absorption spectra is made wherever it is possible and the results obtained favor the distorted fivefold-coordination arrangement for the molecular structure of the Cu(II) ion in aqueous solution.

  • 4.
    Elgammal, Karim
    et al.
    Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Kista, Sweden; SeRC (Swedish e-Science Research Center), KTH Royal Institute of Technology, Stockholm, Sweden.
    Hugosson, Håkan Wilhelm
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Fysik.
    Smith, Anderson D.
    Department of Integrated Devices and Circuits, School of Information and Communication Technology, KTH Royal Institute of Technology, Kista, Sweden; Department of Microtechnology and Nanoscience, Electronics Materials Systems Laboratory, Chalmers Institute of Technology, Gothenburg, Sweden.
    Råsander, Mikael
    Department of Materials, Imperial College London, London, United Kingdom.
    Bergqvist, Lars
    Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Kista, Sweden; SeRC (Swedish e-Science Research Center), KTH Royal Institute of Technology, Stockholm, Sweden.
    Delin, Anna
    Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Kista, Sweden; SeRC (Swedish e-Science Research Center), KTH Royal Institute of Technology, Stockholm, Sweden; Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Uppsala, Sweden.
    Density functional calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substrates2017Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 663, s. 23-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present dispersion-corrected density functional calculations of water and carbon dioxide molecules adsorption on graphene residing on silica and sapphire substrates. The equilibrium positions and bonding distances for the molecules are determined. Water is found to prefer the hollow site in the center of the graphene hexagon, whereas carbon dioxide prefers sites bridging carbon-carbon bonds as well as sites directly on top of carbon atoms. The energy differences between different sites are however minute – typically just a few tenths of a millielectronvolt. Overall, the molecule-graphene bonding distances are found to be in the range 3.1–3.3 Å. The carbon dioxide binding energy to graphene is found to be almost twice that of the water binding energy (around 0.17 eV compared to around 0.09 eV). The present results compare well with previous calculations, where available. Using charge density differences, we also qualitatively illustrate the effect of the different substrates and molecules on the electronic structure of the graphene sheet.

  • 5.
    Grechnev, G. E
    et al.
    Uppsala universitet; Verkin Institute for Low Temperature Physics, Ukraine.
    Hugosson, Håkan Wilhelm
    Uppsala universitet.
    Ahuja, R
    Uppsala universitet.
    Eriksson, O
    Uppsala universitet.
    Structural Evolution and Hardness of Transition Metal Dioxides at High Pressure2000Inngår i: High Pressure Physics and Technology, Vol. 10, nr 38Artikkel i tidsskrift (Fagfellevurdert)
  • 6. Hugosson, Håkan Wilhelm
    A surface coating2000Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    H.W. Hugosson, “A Surface Coating”, SE0004203-6, WO0240734, US2004076856. This patent was developed from predictions and innovations stemming from my long term theoretical work on transition metal carbides and nitrides, coming to an apex in publication VIII and experimentally verified in publication XV. It is arguably one of the earliest examples of a patented innovation based on the results of electronic structure calculations (2000). 

  • 7. Hugosson, Håkan Wilhelm
    Theoretical Studies of Vacancies and Impurities in Molybdenum2000Inngår i: Frontiers in Interdisciplinary Physics, IAPS Press , 2000Kapittel i bok, del av antologi (Fagfellevurdert)
  • 8.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Materials Science, KTH, Lindstedsvägen 23,S-100 44 Stockholm,Sweden.
    Cao, Weimin
    Department of Materials Science, KTH, Lindstedsvägen 23,S-100 44 Stockholm,Sweden.
    Seetharaman, Seshadri
    Department of Materials Science, KTH, Lindstedsvägen 23,S-100 44 Stockholm,Sweden.
    Delin, Anna
    Department of Materials Science, KTH, Lindstedsvägen 23,S-100 44 Stockholm,Sweden;SeRC, KTH, SE-100 44, Stockholm, Sweden;Ångstrom Laboratory, Uppsala University, Uppsala, Sweden.
    Sulfur- and Oxygen-Induced Alterations of the Iron (001) Surface Magnetism and Work Function: A Theoretical Study2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 12, s. 6161-6171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic structure and magnetic properties of atomic sulfur and oxygen adsorbed on the iron (001) surface are examined using density functional theory (DFT). The sulfur/oxygen coverage is considered from a quarter of one monolayer (ML) to a full monolayer. The work function change, magnetic properties, and density of states are determined and compared. We find that the work function increases with sulfur coverage in agreement with experiment. We also find that sulfur interacts strongly with the surface layer and that the magnetic moment of the Fe surface decreases as the sulfur coverage increases. In the case of oxygen adsorption, we find that the magnetic moment of the surface Fe atoms instead increases. We show that the difference in surface magnetic moment between sulfur adsorption and oxygen adsorption can be simply explained combining the Slater–Pauling rigid band model linking d-occupation and magnetic moment with an electronegativity argument. Moreover, the work function of the Fe surface as a function of oxygen coverage is found to be very sensitive to overlayer arrangement, here seen in the cases of 0.5 ML c(2 × 2) and 0.5 ML p(2 × 1). This is shown to result from large differences in the surface dipole moment change induced by the oxygen adsorption in the two different overlayer arrangements.

  • 9.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Engqvist, H
    Sandvik Hard Materials AB.
    The connection between the electronic structure and the properties of binderless tungsten carbides2003Inngår i: International journal of refractory metals & hard materials, ISSN 0263-4368, Vol. 21, nr 1-2, s. 55-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using first principles density functional calculations, we here connect the physical properties of binderless tungsten carbides with the theoretical electronic structure as calculated from density functional theory calculations. We show that electronic structure calculations predict and explain various known phenomena in these systems, an example of how such theoretical studies can be a valuable tool in materials science. For example, changes in the energy of formation from 25% substitution with Mo or Ti is used to explain the differences in intermixing between binderless tungsten carbides using TiC or Mo2C as γ binder phase. Substitutions with Ti atoms are also predicted to stabilize tungsten carbide in the NaCl-structure. A study of the charge density redistribution after substitution is also made.

  • 10.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University; Department of Materials Science and Engineering, Royal Institute of Technology.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Jansson, U.
    Ångström Laboratory, Uppsala University.
    Abrikosov, I.A.
    Department of Physics and Measurement Technology, Linköping University.
    Surface segregation of transition metal impurities on the TiC(100) surface2005Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 585, nr 1-2, s. 101-107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The segregation energies of 3d (Sc–Cu), 4d (Y–Ag) and 5d (La–Au) transition metal impurities on the (1 0 0) surface of TiC have been obtained using first-principles electronic structure calculations. The results are in agreement with available experimental data and show that the difference in atomic size between the impurity and host species, as well as the difference in surface energies determines if the impurity will segregate towards the surface or not. The results indicate that the difference in size is the dominant factor for the trends in segregation of transition metal impurities towards the (1 0 0) surface of TiC.

  • 11.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University; Department of Materials Science and Engineering, Royal Institute of Technology.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Jansson, U.
    Department of Materials Chemistry, Uppsala University.
    Ruban, A.V.
    Center for Atomic-Scale Materials Physics and Department of Physics, Technical University of Denmar.
    Souvatzis, P.
    Department of Physics, Uppsala University.
    Abrikosov, I.A.
    Department of Physics, Uppsala University; Department of Physics and Measurements Technology, Linköping University.
    Surface energies and work functions of the transition metal carbides2004Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 557, nr 1-3, s. 243-254Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have performed an ab initio study of the surface energies, surface electronic structures and work functions for the (1 0 0) surface of the, existent and hypothetical, cubic 3d (Sc–Cu), 4d (Zr–Ag) and 5d (La–Au) transition metal carbides. The calculated surface energies have been compared to predictions using a so-called bond-cutting model and a model based on the so-called bonding energies. The absolute values and rough trends of the surface energies are fairly well predicted within the simple bond-cutting model, as compared to fully self-consistent calculations, while both trends and absolute values are well reproduced within the bonding energy model. The electronic structure (densities of states) of the transition metal carbides at the surface and in the bulk have been calculated. The trends are discussed in relation to the behavior of the surface energy and the work function across the series.

  • 12.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Eriksson, Olle
    Ångström Laboratory, Uppsala University.
    Jansson, Ulf
    Department of Physics, Uppsala University.
    Johansson, Börje
    Department of Physics, Uppsala University.
    Phase stabilities and homogeneity ranges in 4d-transition-metal carbides: A theoretical study2001Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 63, nr 13, artikkel-id 134108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the 4d-transition-metal carbides ZrC, NbC, and MoC. The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC, and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand the differences in phase stabilities and the changes in homogeneity ranges found between these systems is explained. The results can be regarded as theoretical zero-temperature phase stability diagrams for the three compounds containing not only the experimentally verified but also hypothetical phases and many of the experimental properties and trends are reproduced and explained. A study of the changes and differences in electronic structure and bonding of the studied compounds, phases and stoichiometries is also presented. As a part of this study the hexagonal Me2C (Me being Zr, Nb, or Mo) phases were studied and the theoretical structures, with relaxed interlayer distances and lattice parameters, were obtained. The phase stabilities and electronic structure of the experimentally reported orthorhombic Nb2C and Mo2C phases were also studied.

  • 13.
    Hugosson, Håkan Wilhelm
    et al.
    Uppsala universitet.
    Eriksson, Olle
    Uppsala universitet.
    Nordström, Lars
    Uppsala universitet.
    Jansson, Ulf
    Fast, Lars
    Ångström Laboratory, Uppsala universitet.
    Delin, Anna
    Ångström Laboratory, Uppsala universitet.
    Wills, John M.
    Los Alamos National Laboratory, Los Alamos, New Mexico.
    Johansson, Börje
    Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide1999Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, nr 7, s. 3758-3767Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ABSTRACTFirst principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic δ(NaCl) phase and the three hexagonal γ(WC), η and γ′(TiAs) phases. The effect of vacancies on the relative stability of these four phases was investigated using a model structure with ordered vacancies within the carbon sublattice. For stoichiometric MoC, the γ phase was found to be the most stable followed by γ′, δ, and η, but for substoichiometric MoC0.75,MoC0.75, the order of relative stability was changed and the substoichiometric δ phase was found to have the lowest energy followed by γ′ and γ. A study of the electronic structure revealed vacancy induced peaks in the density of state and the electron density attached to these peaks was analyzed and found to emanate from unscreened Mo–Mo bonds through the carbon vacancy site. Finally, the oxygen stabilization of the γ′ MoC phase was studied.

  • 14.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Grechnev, G. E.
    Department of Physics, Uppsala University.
    Ahuja, R.
    Department of Physics, Uppsala University.
    Helmersson, U.
    Department of Physics, Linköping University.
    Sa, L.
    Department of Physics, Uppsala University.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Stabilization of potential superhard RuO2 phases: A theoretical study2002Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 66, nr 17, artikkel-id 174111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study RuO2 in the fluorite (CaF2) and rutile structures. An investigation of the effects of metal and nonmetal alloying, oxygen vacancies, and lattice strain on the phase stabilities and electronic structure has been made. From these theoretical results suggestions on how the cubic phase may be stabilized are made. The pressure induced phase transitions between the rutile, CaCl2, Pa3 and fluorite phases and the bulk moduli of several 4d and 5d transition metal dioxides have also been studied.

  • 15.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Högberg, H.
    Sandvik Coromant AB.
    Algren, M.
    Sandvik Coromant AB.
    Rodmar, M.
    Sandvik Coromant AB.
    Selinder, T. I.
    Sandvik Coromant AB.
    Theory of the effects of substitutions on the phase stabilities of Ti1−xAlxN2003Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 8, s. 4505-4511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have performed ab initio studies of the effect of substitutions on the phase stabilities of Ti1−xAl𝑥N,Ti1−xAlxN, x=0−1.x=0−1. The nonmetal substitutions studied include B, C, O, and Si. Metal substitutions studied include Sc, Zr, V, Cr, and Mn. The main objective has been to suggest substitutions that increase the thermal stability of the NaCl structure of Ti1−xAl𝑥NTi1−xAlxN at high Al contents. From these extensive and consistent calculations, some possible avenues for such stabilization present themselves, among which substitution with nonmetal C and Si, and metal V, Cr, and Mn are found to be the most promising.

  • 16.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Jansson, U.
    Ångström Laboratory, Uppsala University.
    Johansson, B.
    Department of Physics, Uppsala University.
    Eriksson, O.
    Department of Physics, Uppsala University.
    Phase stability diagrams of transition metal carbides, a theoretical study2001Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 333, nr 6, s. 444-450Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand, for example, the differences and changes in homogeneity ranges found in these systems. This determination of relative phase stabilities for a wide range of concentrations is necessary for first principles determination of phase diagrams for these compounds with complex bonding and structural properties as well as technological importance.

  • 17.
    Hugosson, Håkan Wilhelm
    et al.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden..
    Jansson, Ulf
    Department of Materials Chemistry, Ångström Laboratory, Uppsala University, Box 538, S-751 21 Uppsala, Sweden..
    Johansson, Börje
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden.;Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, S-100 44 Stockholm, Sweden..
    Eriksson, Olle
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden..
    Restricting Dislocation Movement in Transition Metal Carbides by Phase Stability Tuning2001Inngår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 293, nr 5539, s. 2434-2437Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mechanism to enhance hardness in multilayer coatings is proposed. Using the technologically important hard transition metal carbides as prototypes, although the principle is transferable also to other systems, we demonstrate, from first-principles calculations, that by suitable alloying the energy difference between several competing structures in the transition metal carbides is small or tunable. This creates multiphase/polytypic compounds with a random or controllable layer stacking sequence, systems in which the propagation of dislocations can be strongly suppressed by a large number of interfaces between structures with different glide systems, accordingly allowing the possibility of a greatly enhanced hardness. With modern thin-film technologies, it should therefore be possible to deposit such materials that will express multilayer characteristics with only minor changes in the chemical constitution of the material, which is in contrast to conventional superlattices.

  • 18. Hugosson, Håkan Wilhelm
    et al.
    Johansson, B
    Eriksson, O
    Theoretical Studies of Sub-Stoichiometric MoC(1-x)1999Inngår i: Proceedings of the International Conference on Solid-Solid Phase Transformations '99, 1999Konferansepaper (Fagfellevurdert)
  • 19.
    Hugosson, Håkan Wilhelm
    et al.
    Department of Physics, Uppsala University.
    Korzhavyi, Pavel
    Department of Materials and Engineering, Royal Institute of Technology, Sweden.
    Jansson, Ulf
    Ångström Laboratory, Uppsala University.
    Johansson, Börje
    Department of Physics, Uppsala University; erials and Engineering, Royal Institute of Technology, Sweden.
    Eriksson, Olle
    Department of Physics, Uppsala University.
    Phase stabilities and structural relaxations in substoichiometric TiC1−x2001Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 63, nr 16, artikkel-id 165116Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1−x. The effect of relaxation on phase stabilities, equilibrium volumes, and electronic structure of the substoichiometric phases was studied using a combined approach of pseudopotential plane wave and full-potential linear muffin-tin orbital methods. A relaxation away from the vacancies was found for the titanium atoms, the magnitude of which increased with vacancy concentration and the inclusion of nearest-neighbor carbon atom relaxation. The inclusion of local relaxations was found to correctly predict the off-stoichiometric equilibrium composition of titanium carbide. The anomalous volume behavior of TiC at small vacancy concentration is explained as an effect of the local relaxation of the atoms surrounding the vacancy sites, but we do not find that the lattice parameter of any of the studied stoichiometries is larger than that of ideal stoichiometric TiC.

  • 20.
    Hugosson, Håkan Wilhelm
    et al.
    Laboratory of Computational Chemistry and Biochemistry, Institute of Molecular and BiologicalChemistry, Swiss Federal Institute of Technology EPF Lausanne, Switzerland.
    Laio, Alessandro
    CSCS Science Division, Via Cantonale, 6928 Manno, Switzerland.
    Maurer, Patrick
    Laboratory of Inorganic Chemistry, Swiss Federal Institute of Technology ETH Zürich, Switzerland.
    Rothlisberger, Ursula
    Laboratory of Computational Chemistry and Biochemistry, Institute of Molecular and BiologicalChemistry, Swiss Federal Institute of Technology EPF Lausanne, Switzerland.
    A comparative theoretical study of dipeptide solvation in water2006Inngår i: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 27, nr 5, s. 672-684Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics studies have been performed on the zwitterionic form of the dipeptide glycine–alanine in water, with focus on the solvation and electrostatic properties using a range of theoretical methods, from purely classical force fields, through mixed quantum mechanical/molecular mechanical simulations, to fully quantum mechanical Car–Parrinello calculations. The results of these studies show that the solvation pattern is similar for all methods used for most atoms in the dipeptide, but can differ substantially for some groups; namely the carboxy and aminoterminii, and the backbone amid NH group. This might have implications in other theoretical studies of peptides and proteins with charged —NH  and —CO  side chains solvated in water. Hybrid quantum mechanical/molecular mechanical simulations successfully reproduce the solvation patterns from the fully quantum mechanical simulations (PACS numbers: 87.14.Ee, 87.15.Aa, 87.15.He, 71.15.Pd).

  • 21.
    Hugosson, Håkan Wilhelm
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Mirsakiyeva, A
    Ab Inition Molecular Dynamics on Conjugated Polymers: Localization of the PolaronManuskript (preprint) (Annet vitenskapelig)
  • 22.
    Hugosson, Håkan Wilhelm
    et al.
    Uppsala universitet.
    Nordström, Lars
    Uppsala universitet.
    Jansson, Ulf
    Uppsala universitet.
    Johansson, Börje
    Uppsala universitet.
    Eriksson, Olle
    Uppsala universitet.
    Theoretical studies of substitutional impurities in molybdenum carbide1999Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, nr 22, s. 15123-15130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the effect on the cohesion and electronic structure of cubic δ-MoC when 25% of the carbon is substituted for boron, nitrogen, or oxygen and when 25% of the molybdenum is substituted for niobium, tungsten, or ruthenium. A thorough study of the changes in the electronic structure and the effect of these on the properties of the compounds is made. Special attention is paid to the character (ionic, covalent, or metallic) of the states becoming occupied (or unoccupied) due to the substitution. A study is also made on the properties of the quaternary alloy Mo0.75W0.25C0.75N0.25. This substitution is shown to harden δ-MoC.

  • 23. Hugosson, Håkan Wilhelm
    et al.
    Ågren, H
    Quantum Mechanical / Molecular Mechanical Modeling of Biological Systems2009Inngår i: Multiscale Modeling and Simulation in Science / [ed] B. Engquist, P. Lötstedt, and O. Runborg, Springer , 2009, s. 291-294Kapittel i bok, del av antologi (Fagfellevurdert)
  • 24.
    Joelsson, T.
    et al.
    Department of Physics and Measurement Technology, IFM, Linköping University.
    Hultman, L.
    Department of Physics and Measurement Technology, IFM, Linköping University.
    Hugosson, Håkan Wilhelm
    Department of Physics, Uppsala University.
    Molina-Aldareguia, J. M.
    CEIT (Centro de Estudios e Investigaciones Técnicas de Gipuzkoa) , San Sebastian, Spain.
    Phase stability tuning in the NbxZr1−xN thin-film system for large stacking fault density and enhanced mechanical strength2005Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, nr 13, artikkel-id 131922Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase stability of hexagonal WC-structure and cubic NaCl-structure 4𝑑4d transition metal nitrides was calculated using first-principles density functional theory. It is predicted that there is a multiphase or polytypic region for the 4𝑑4d transition metal nitrides with a valence electron concentration around 9.5 to 9.7 per formula unit. For verification, epitaxial Nb𝑥Zr1−𝑥NNbxZr1−xN (0⩽𝑥⩽1)(0⩽x⩽1) was grown by reactive magnetron sputter deposition on MgO(001) substrates and analyzed with transmission electron microscopy (TEM) and x-ray diffraction. The defects observed in the films were threading dislocations due to nucleation and growth on the lattice-mismatched substrate and planar defects (stacking faults) parallel to the substrate surface. The highest defect density was found at the 𝑥=0.5x=0.5 composition. The nanoindentation hardness of the films varied between 21GPa21GPa for the binary nitrides, and 26GPa26GPa for Nb0.5Zr0.5NNb0.5Zr0.5N. Unlike the cubic binary nitrides, no slip on the preferred ⟨11¯0⟩{110}⟨11¯0⟩{110} slip system was observed. The increase in hardness is attributed to the increase in defect density at 𝑥=0.5x=0.5, as the defects act as obstacles for dislocation glide during deformation. The findings present routes for the design of wear-resistant nitride coatings by phase stability tuning.The authors acknowledge support from the Swedish Research Council (VR) and the Foundation for Strategic Research (SSF) Materials Research program on Low-temperature Thin Film synthesis. Jörg Neidhardt is acknowledged for assistance with the hardness measurements.

  • 25.
    Korzhavyi, Pavel A.
    et al.
    KTH.
    Pourovskii, Leonid V.
    Department of Physics, Uppsala University.
    Hugosson, Håkan Wilhelm
    Uppsala University.
    Ruban, Andrei V.
    Technical University of Denmark.
    Johansson, Börje
    KTH.
    Ab Initio Study of Phase Equilibria in TiCx2002Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 88, nr 1, s. 015505-1-01505-4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase diagram for the vacancy-ordered structures in the substoichiometric TiCx (x=0.5-1.0) has been established from Monte Carlo simulations with the long-range pair and multisite effective interactions obtained from ab initio calculations. Three ordered superstructures of vacancies (Ti2C, Ti3C2, and Ti6C5) are found to be ground state configurations. Their stability has been verified by full-potential total energy calculations of the fully relaxed structures.

  • 26.
    Lu, J
    et al.
    Department of Inorganic Chemistry, Ångström Laboratory, University of Uppsala, Box 538, S-751 21 Uppsala, Sweden.
    Hugosson, Håkan Wilhelm
    Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, S-751 21, Uppsala, Sweden.
    Eriksson, O
    Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, S-751 21, Uppsala, Sweden.
    Nordström, L
    Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, S-751 21, Uppsala, Sweden.
    Jansson, U
    Department of Inorganic Chemistry, Ångström Laboratory, University of Uppsala, Box 538, S-751 21 Uppsala, Sweden.
    Chemical vapour deposition of molybdenum carbides: aspects of phase stability2000Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 370, nr 1-2, s. 203-212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin films of different molybdenum carbides (δ-MoC1−x, γ′-MoC1−x and Mo2C) have been deposited from a gas mixture of MoCl5/H2/C2H4 at 800°C by CVD. The H2 content in the vapour has a strong influence on the phase composition and microstructure. Typically, high H2 contents lead to the formation of nanocrystalline δ-MoC1−x films while coarse-grained γ′-MoC1−x is formed with an H2-free gas mixture. This phase has previously only been synthesized by carburization of Mo in a CO atmosphere and it has therefore been considered as an oxycarbide phase stabilized by the presence of oxygen in the lattice. Our results, however, show that γ′-MoC1−x films containing only trace amounts of oxygen can be deposited by CVD. Stability calculations using a FP-LMTO method confirmed that the γ′-MoC1−x phase is stabilized by oxygen but that the difference in energy between e.g. δ-MoC0.75 and oxygen-free γ′-MoC0.75 is small enough to allow the synthesis of the latter phase in the absence of kinetic constraints. Annealing experiments of metastable δ-MoC1−x and γ′-MoC1−x films showed two different reaction products suggesting that kinetic effects play an important role in the decomposition of these phases.

  • 27.
    Mattesini, M.
    et al.
    Departamento de Física de la Tierra, Astronomía y Astrofísica I, Universidad Complutense de Madrid, E-28040 Madrid, Spain.
    Ahuja, R.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden; KTH.
    Sa, L.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden.
    Hugosson, Håkan Wilhelm
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden.
    Johansson, B.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden; KTH.
    Eriksson, O.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden.
    Electronic structure and optical properties of solid C602009Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 404, nr 12-13, s. 1776-1780Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic structure and the optical properties of face-centered-cubic C60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis–UV absorption spectrum of solid C60.

  • 28.
    Maurer, Patrick
    et al.
    École Polytechnique Fédérale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, BCH-LCBC, CH-1015 Lausanne, Switzerland.
    Laio, Alessandro
    École Polytechnique Fédérale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, BCH-LCBC, CH-1015 Lausanne, Switzerland.
    Hugosson, Håkan Wilhelm
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik. École Polytechnique Fédérale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, BCH-LCBC, CH-1015 Lausanne, Switzerland.
    Colombo, Maria Carola
    École Polytechnique Fédérale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, BCH-LCBC, CH-1015 Lausanne, Switzerland.
    Rothlisberger, Ursula
    École Polytechnique Fédérale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, BCH-LCBC, CH-1015 Lausanne, Switzerland.
    Automated Parametrization of Biomolecular Force Fields from Quantum Mechanics/Molecular Mechanics (QM/MM) Simulations through Force Matching2007Inngår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 3, nr 2, s. 628-639Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We introduce a novel procedure to parametrize biomolecular force fields. We perform finite-temperature quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations, with the fragment or moiety that has to be parametrized being included in the QM region. By applying a force-matching algorithm, we derive a force field designed in order to reproduce the steric, electrostatic, and dynamic properties of the QM subsystem. The force field determined in this manner has an accuracy that is comparable to the one of the reference QM/MM calculation, but at a greatly reduced computational cost. This allows calculating quantities that would be prohibitive within a QM/MM approach, such as thermodynamic averages involving slow motions of a protein. The method is tested on three different systems in aqueous solution:  dihydrogenphosphate, glycyl−alanine dipeptide, and a nitrosyl−dicarbonyl complex of technetium(I). Molecular dynamics simulations with the optimized force field show overall excellent performance in reproducing properties such as structures and dipole moments of the solutes as well as their solvation pattern.

  • 29. Mirsakiyeva, A
    et al.
    Delin, A
    Hugosson, Håkan Wilhelm
    Quantum Molecular Dynamics Studies of Thermoelectric Polymer Systems2015Konferansepaper (Fagfellevurdert)
  • 30.
    Mirsakiyeva, Amina
    et al.
    KTH; Kazakh-British Technical University, Almaty, Kazakhstan.
    Botkina, Darya
    KTH; Institute of Chemical Sciences, Almaty, Kazakhstan.
    Elgammal, Karim
    KTH.
    Ten, Assel
    Kazakh-British Technical University, Almaty, Kazakhstan.
    Hugosson, Håkan Wilhelm
    KTH.
    Delin, Anna
    KTH; Uppsala University.
    Yu, Valentina
    KTH; Institute of Chemical Sciences, Almaty, Kazakhstan.
    Experimental and density functional theory studies of some novel piperidine-containing acetylene glycols2016Inngår i: ARKIVOC, ISSN 1551-7004, E-ISSN 1551-7012, s. 86-99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synthesis routes of novel piperidine-containing acetylenes are presented. The new molecules are expected to exhibit plant growth stimulation properties. In particular, the yield in a situation of drought is expected to increase. Our synthesis makes use of the Favorskii reaction between cyclohexanone/piperidone and triple-bond containing alcohols. The structures of the obtained molecules were determined using nuclear magnetic resonance (NMR). The electronic structure and geometries of the molecules were studied theoretically using first-principles calculations based on density functional theory. The calculated geometries agree very well with the experimentally determined ones, and also allow us to determine bond lengths, angles and charge distributions inside the molecules.

  • 31. Mirsakiyeva, Amina
    et al.
    Botkina, Darya
    Elgammal, Karim
    Ten, Assel
    Hugosson, Håkan Wilhelm
    Delin, Anna
    Yu, Valentina K
    Experimental and ab initio studies of the novel piperidine-containing acetylene glycolsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Synthesis routes of novel piperidine-containing diacetylene are presented. The new molecules are expected to exhibit plant growth stimulation properties. In particular, the yield in a situation of drought is expected to increase. The synthesis makes use of the Favorskii reaction between cycloketones/piperidone and triple-bond containing glycols. The geometries of the obtained molecules were determined using nuclear magnetic resonance (NMR). The electronic structure and geometries of the molecules were studied theoretically using first-principles calculations based on density functional theory. The calculated geometries agree very well with the experimentally measured ones, and also allow us to determine bond lengths, angles and charge distributions inside the molecules. The stability of the OH-radicals located close to the triple bond and the piperidine/cyclohexane rings was proven by both experimental and theoretical analyses. The HOMO/LUMO analysis was done in order to characterize the electron density of the molecule. The calculations show that triple bond does not participate in intermolecular reactions which excludes the instability of novel materials as a reason for low production rate.

  • 32.
    Mirsakiyeva, Amina
    et al.
    Material and Nanophysics Department, KTH Royal Institute of Technology, Kista, Sweden.
    Hugosson, Håkan Wilhelm
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Fysik. Material and Nanophysics Department, KTH Royal Institute of Technology, Kista, Sweden.
    Crispin, Xavier
    Linköpings universitet.
    Delin, Anna
    Material and Nanophysics Department, KTH Royal Institute of Technology, Kista, Sweden; Swedish e-Science Research Center, KTH, Stockholm, Sweden; Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Quantum Molecular Dynamical Calculations of PEDOT 12-Oligomer and its Selenium and Tellurium Derivatives2017Inngår i: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 46, nr 5, s. 3071-3075Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present simulation results, computed with the Car–Parrinello molecular dynamics method, at zero and ambient temperature (300 K) for poly(3,4-ethylenedioxythiophene) [PEDOT] and its selenium and tellurium derivatives PEDOS and PEDOTe, represented as 12-oligomer chains. In particular, we focus on structural parameters such as the dihedral rotation angle distribution, as well as how the charge distribution is affected by temperature. We find that for PEDOT, the dihedral angle distribution shows two distinct local maxima whereas for PEDOS and PEDOTe, the distributions only have one clear maximum. The twisting stiffness at ambient temperature appears to be larger the lighter the heteroatom (S, Se, Te) is, in contrast to the case at 0 K. As regards point charge distributions, they suggest that aromaticity increases with temperature, and also that aromaticity becomes more pronounced the lighter the heteroatom is, both at 0 K and ambient temperature. Our results agree well with previous results, where available. The bond lengths are consistent with substantial aromatic character both at 0 K and at ambient temperature. Our calculations also reproduce the expected trend of diminishing gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital with increasing atomic number of the heteroatom.

    Fulltekst (pdf)
    fulltext
  • 33.
    Mirsakiyeva, Amina
    et al.
    Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Kista, Sweden.
    Hugosson, Håkan Wilhelm
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Fysik.
    Linares, Mathieu
    Department Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, Stockholm, Sweden; 4Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, Stockholm, Sweden.
    Delin, Anna
    Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Kista, Sweden; Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, Stockholm, Sweden; Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Uppsala, Sweden.
    Temperature dependence of band gaps and conformational disorder in PEDOT and its selenium and tellurium derivatives: Density functional calculations2017Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, nr 13, artikkel-id 134906Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The conducting polymer poly(3,4-ethylenedioxythiophene), or PEDOT, is an attractive material for flexible electronics. We present combined molecular dynamics and quantum chemical calculations, based on density functional theory, of EDOT oligomers and isoelectronic selenium and tellurium derivatives (EDOS and EDOTe) to address the effect of temperature on the geometrical and electronic properties of these systems. With finite size scaling, we also extrapolate our results to the infinite polymers, i.e., PEDOT, PEDOS, and PEDOTe. Our computations indicate that the most favourable oligomer conformations at finite temperature are conformations around the flat trans-conformation and a non-flat conformation around 45° from the cis-conformation. Also, the dihedral stiffness increases with the atomic number of the heteroatom. We find excellent agreement with experimentally measured gaps for PEDOT and PEDOS. For PEDOT, the gap does not increase with temperature, whereas this is the case for its derivatives. The conformational disorder and the choice of the basis set both significantly affect the calculated gaps.

  • 34.
    Murugan, N. Arul
    et al.
    KTH.
    Hugosson, Håkan Wilhelm
    KTH.
    Investigations into conformational transitions and solvation structure of a 7-piperidino-5,9-methanobenzo[8] annulene in water2008Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 10, nr 40, s. 6135-6135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solvation shell structure of a 7-piperidino-5,9-methanobenzo[8] annulene (PMA) in water has been investigated in ambient conditions using both molecular dynamics (MD) and Car-Parrinello molecular dynamics (CPMD) calculations. From the MD calculations, we find that this molecule exists in three major conformational states out of which two are in twist-boat forms and one in chair form. Due to the limited time scale accessible in CPMD simulations, we have studied all the three conformational states separately using CPMD. The molecular geometry, electronic charge distribution and solvation structure for all three forms are investigated. The stability order of the chair and twist-boat conformations in water solvent has been reversed when compared to the gaseous phase results and in the case of polar aprotic solvents (J. Org. Chem., 1999, 61, 5979). From the radial distribution function, we find that the solvent density around the chair form is significantly lower, which has to be directly related to the smaller solvent accessible area for this conformation and this is in complete agreement with earlier reports. Among the findings are that the solvation shell structure around the nitrogen atom in the chair form of PMA is considerably different from the open conformational forms or the twist-boat forms. The dipole moment for the closed form is found to be significantly larger when compared to the twist-boat forms.

  • 35.
    Murugan, N. Arul
    et al.
    Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden.
    Hugosson, Håkan Wilhelm
    Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden.
    Solvent Dependence of Conformational Distribution, Molecular Geometry, and Electronic Structure in Adenosine2009Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, nr 4, s. 1012-1021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solvation dynamics of adenosine in water and chloroform solvents under ambient conditions has been investigated using both force-field molecular dynamics (MD) and first-principles Car−Parrinello molecular dynamics (CPMD) calculations. First, the solvent dependence of the equilibria between anti−syn forms, C(3′)-endo−C(2′)−endo conformations, and carbinol group rotamers has been discussed from MD calculations. We find that in both the solvents the adenosine molecule can remain either in anti or syn conformations. But, the anti−syn interconversion occurs relatively faster in water solvent than in chloroform solvent. Because of the relatively larger time scale for the interconversion, anti and syn conformational states of adenosine are studied separately in water and chloroform solvents using CPMD calculations. The dipole moments calculated from CPMD and MD calculations for adenosine in water are significantly larger than in chloroform solvent. On the basis of the CPMD calculations, the syn form of adenosine in water has a larger dipole moment than the anti form. Moreover, the molecular geometry of anti and syn forms of adenosine in these two solvents is reported. We report a remarkable solvent effect on the geometry of the anti form of the adenosine, which is attributed to differences in the intermolecular and intramolecular hydrogen-bonding stabilization. We also report the solvent effect on the frontier Kohn−Sham orbitals and energy gaps for anti−syn conformational states. Finally, we report the solvation shell structure of adenosine in both the solvents, and we find that the solvent−solute interaction is site-specific in the case of water while in chloroform solvent the interaction is globular isotropic in nature.

  • 36.
    Murugan, N. Arul
    et al.
    Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden.
    Hugosson, Håkan Wilhelm
    Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden.
    Ågren, Hans
    Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden.
    Solvent Dependence on Conformational Transition, Dipole Moment, and Molecular Geometry of 1,2-Dichloroethane: Insight from Car−Parrinello Molecular Dynamics Calculations2008Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, nr 47, s. 14673-14677Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the molecular geometry and dipole moment distribution for the major conformational states of 1,2-dichloroethane (DCE) in three different solvents under ambient conditions using the Car−Parrinello mixed quantum mechanics/molecular mechanics method. The solvents studied were water, DCE, and chloroform. Within the time scale investigated, we find a conformational equilibrium existing between the gauche and trans forms of DCE in all three solvents. In the chloroform solvent, the conformational transition occurs more frequently than in water solvent and in liquid DCE (i.e., DCE solute in DCE solvent). The population of gauche conformer is more in the case of water solvent, while the trans conformer dominates in chloroform solvent. We report a bimodal nature of the dipole moment distribution for DCE in all three solute−solvents studied, where the peaks are attributed to the trans and gauche conformational states. The dipole moments of both of the conformational states increase with increasing polarity of the solvent. Also, with an increase in solvent polarity, an increase in the C−Cl bond length and magnitude of atomic charges in DCE has been observed. The increase in atomic charges of DCE is almost twice when the solvent is changed from chloroform to water.

  • 37.
    Råsander, Mikael
    et al.
    Department of Materials, Imperial College London, London, UK.
    Hugosson, Håkan Wilhelm
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Fysik.
    Delin, Anna
    Department of Applied Physics, Kungliga Tekniska Hogskolan, Stockholm, Sweden.
    Density functional study of carbon vacancies in titanium carbide2018Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, nr 1, artikkel-id 015702Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is well established that TiC contains carbon vacancies not only in carbon-deficient environments but also in carbon-rich environments. We have performed density functional calculations of the vacancy formation energy in TiC for C- as well as Ti-rich conditions using several different approximations to the exchange-correlation functional, and also carefully considering the nature and thermodynamics of the carbon reference state, as well as the effect of varying growth conditions. We find that the formation of carbon vacancies is clearly favorable under Ti-rich conditions, whereas it is slightly energetically unfavorable under C-rich conditions. Furthermore, we find that the relaxations of the atoms close to the vacancy site are rather long-ranged, and that these relaxations contribute significantly to the stabilization of the vacancy. Since carbon vacancies in TiC are experimentally observed also in carbon-rich environments, we conclude that kinetics may play an important role. This conclusion is consistent with the experimentally observed high activation energies and sluggish diffusion of vacancies in TiC, effectively causing a freezing in of the vacancies.&#13.

  • 38.
    Schyman, Patric
    et al.
    Arrhenius Laboratory, Stockholm University.
    Laaksonen, Aatto
    Arrhenius Laboratory, Stockholm University.
    Hugosson, Håkan Wilhelm
    KTH.
    Phosphodiester bond rupture in 5′ and 3′ cytosine monophosphate in aqueous environment and the effect of low-energy electron attachment: A Car–Parrinello QM/MM molecular dynamics study2008Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 462, nr 4-6, s. 289-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study we have explored the effect of low-energy electrons (LEEs) when rupturing the C3′–O3′ and C5′–O5′ bonds in 3′ and 5′ cytosine monophosphate in an aqueous environment. This has been done using a hybrid quantum mechanics/classical mechanics (QM/MM) setup within the framework of Car–Parrinello molecular dynamics (CPMD). Our results are in agreement with experimental findings and indicate that LEEs do not drastically lower the energy barrier for breaking the 3′ or 5′ phosphodiester bonds for single cytosine nucleotides in aqueous environment.

  • 39.
    Smith, Anderson D.
    et al.
    KTH Royal Institute of Technology; Department of EKT;School of Information and Communication Technology;SE-16440 Kista, Sweden.
    Elgammal, Karim
    KTH Royal Institute of Technology; Department of Materials and Nano Physics;School of Information and Communication Technology;SE-16440 Kista, Sweden.
    Niklaus, Frank
    KTH Royal Institute of Technology; Department of Micro and Nano Systems;School of Electrical Engineering;SE-10044 Stockholm, Sweden.
    Delin, Anna
    KTH Royal Institute of Technology; Department of Materials and Nano Physics;School of Information and Communication Technology;SE-16440 Kista, Sweden;Uppsala University.
    Fischer, Andreas C.
    KTH Royal Institute of Technology; Department of Micro and Nano Systems;School of Electrical Engineering;SE-10044 Stockholm, Sweden.
    Vaziri, Sam
    KTH Royal Institute of Technology; Department of EKT;School of Information and Communication Technology;SE-16440 Kista, Sweden.
    Forsberg, Fredrik
    KTH Royal Institute of Technology; Department of Micro and Nano Systems;School of Electrical Engineering;SE-10044 Stockholm, Sweden.
    Råsander, Mikael
    KTH Royal Institute of Technology; Department of Materials and Nano Physics;School of Information and Communication Technology;SE-16440 Kista, Sweden;Department of Materials.
    Hugosson, Håkan Wilhelm
    KTH Royal Institute of Technology; Department of Materials and Nano Physics;School of Information and Communication Technology;SE-16440 Kista, Sweden.
    Bergqvist, Lars
    KTH Royal Institute of Technology; Department of Materials and Nano Physics;School of Information and Communication Technology;SE-16440 Kista, Sweden;SeRC (Swedish e-Science Research Center).
    Schröder, Stephan
    KTH Royal Institute of Technology; Department of Micro and Nano Systems;School of Electrical Engineering;SE-10044 Stockholm, Sweden.
    Kataria, Satender
    University of Siegen, 57076 Siegen, Germany.
    Östling, Mikael
    KTH Royal Institute of Technology; Department of EKT; School of Information and Communication Technology;SE-16440 Kista, Sweden.
    Lemme, Max C.
    KTH Royal Institute of Technology; Department of EKT;School of Information and Communication Technology;SE-16440 Kista, Sweden;University of Siegen.
    Resistive graphene humidity sensors with rapid and direct electrical readout2015Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, nr 45, s. 19099-19109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further investigate the sensitivity of the graphene devices towards water vapor. The interaction between the electrostatic dipole moment of the water and the impurity bands in the SiO2 substrate leads to electrostatic doping of the graphene layer. The proposed graphene sensor provides rapid response direct electrical readout and is compatible with back end of the line (BEOL) integration on top of CMOS-based integrated circuits.

1 - 39 of 39
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