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Hugosson, Håkan WilhelmORCID iD iconorcid.org/0000-0001-8748-3890
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Råsander, M., Hugosson, H. W. & Delin, A. (2018). Density functional study of carbon vacancies in titanium carbide. Journal of Physics: Condensed Matter, 30(1), Article ID 015702.
Öppna denna publikation i ny flik eller fönster >>Density functional study of carbon vacancies in titanium carbide
2018 (Engelska)Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, nr 1, artikel-id 015702Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Carbon vacancies, Density functional theory, Titanium carbide
Nationell ämneskategori
Fysik Materialteknik
Identifikatorer
urn:nbn:se:hig:diva-25596 (URN)10.1088/1361-648X/aa9979 (DOI)000423884100012 ()29120870 (PubMedID)2-s2.0-85038602593 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetEnergimyndighetenCarl Tryggers stiftelse för vetenskaplig forskning
Tillgänglig från: 2017-11-24 Skapad: 2017-11-24 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Elgammal, K., Hugosson, H. W., Smith, A. D., Råsander, M., Bergqvist, L. & Delin, A. (2017). Density functional calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substrates. Surface Science, 663, 23-30
Öppna denna publikation i ny flik eller fönster >>Density functional calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substrates
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2017 (Engelska)Ingår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 663, s. 23-30Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Graphene; DFT; Sensor; Humidity; Carbon dioxide
Nationell ämneskategori
Materialteknik
Identifikatorer
urn:nbn:se:hig:diva-24190 (URN)10.1016/j.susc.2017.04.009 (DOI)000405043300004 ()2-s2.0-85018431677 (Scopus ID)
Tillgänglig från: 2017-06-13 Skapad: 2017-06-13 Senast uppdaterad: 2022-11-09Bibliografiskt granskad
Mirsakiyeva, A., Hugosson, H. W., Crispin, X. & Delin, A. (2017). Quantum Molecular Dynamical Calculations of PEDOT 12-Oligomer and its Selenium and Tellurium Derivatives. Paper presented at 35th International Conference on Thermoelectrics (ICT), Wuhan, China, 2016. Journal of Electronic Materials, 46(5), 3071-3075
Öppna denna publikation i ny flik eller fönster >>Quantum Molecular Dynamical Calculations of PEDOT 12-Oligomer and its Selenium and Tellurium Derivatives
2017 (Engelska)Ingår i: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 46, nr 5, s. 3071-3075Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Aromatization; Atoms; Charge distribution; Density functional theory; Molecular dynamics; Molecular orbitals; Selenium; Tellurium; Tellurium compounds; Temperature, Dynamical calculations; Highest occupied molecular orbital; Lowest unoccupied molecular orbital; Molecular dynamics methods; PEDOS; PEDOT; PEDOTe; Poly-3, 4-ethylenedioxythiophene, Dihedral angle
Nationell ämneskategori
Elektroteknik och elektronik
Identifikatorer
urn:nbn:se:hig:diva-23282 (URN)10.1007/s11664-016-5161-6 (DOI)000398937900075 ()2-s2.0-85001037983 (Scopus ID)
Konferens
35th International Conference on Thermoelectrics (ICT), Wuhan, China, 2016
Forskningsfinansiär
VetenskapsrådetKungliga VetenskapsakademienKnut och Alice Wallenbergs StiftelseCarl Tryggers stiftelse för vetenskaplig forskning Energimyndigheten
Anmärkning

Funders: Vetenskapsradet (VR), The Royal Swedish Academy of Sciences (KVA), the Knut and Alice Wallenberg Foundation (KAW), Carl Tryggers Stiftelse (CTS), Swedish Energy Agency (STEM), Swedish Foundation for Strategic Research (SSF), and Erasmus Mundus Action 2 TARGET II consortium

Tillgänglig från: 2017-01-12 Skapad: 2017-01-11 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Mirsakiyeva, A., Hugosson, H. W., Linares, M. & Delin, A. (2017). Temperature dependence of band gaps and conformational disorder in PEDOT and its selenium and tellurium derivatives: Density functional calculations. Journal of Chemical Physics, 147(13), Article ID 134906.
Öppna denna publikation i ny flik eller fönster >>Temperature dependence of band gaps and conformational disorder in PEDOT and its selenium and tellurium derivatives: Density functional calculations
2017 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, nr 13, artikel-id 134906Artikel i tidskrift (Refereegranskat) Published
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.

Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:hig:diva-25412 (URN)10.1063/1.4998509 (DOI)000412321600030 ()28987116 (PubMedID)2-s2.0-85031789300 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetKungliga VetenskapsakademienKnut och Alice Wallenbergs StiftelseCarl Tryggers stiftelse för vetenskaplig forskning Energimyndigheten
Anmärkning

Ytterligare finansiär:

Swedish Foundation for Strategic Research (SSF) 

Tillgänglig från: 2017-10-16 Skapad: 2017-10-16 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Mirsakiyeva, A., Botkina, D., Elgammal, K., Ten, A., Hugosson, H. W., Delin, A. & Yu, V. (2016). Experimental and density functional theory studies of some novel piperidine-containing acetylene glycols. ARKIVOC, 86-99
Öppna denna publikation i ny flik eller fönster >>Experimental and density functional theory studies of some novel piperidine-containing acetylene glycols
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2016 (Engelska)Ingår i: ARKIVOC, ISSN 1551-7004, E-ISSN 1551-7012, s. 86-99Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Arkat, 2016
Nyckelord
Piperidine, acetylene glycols, CPMD, MD, density functional theory, plant growth stimulation
Nationell ämneskategori
Organisk kemi
Identifikatorer
urn:nbn:se:hig:diva-40382 (URN)10.3998/ark.5550190.p009.452 (DOI)000377613000007 ()2-s2.0-84973097501 (Scopus ID)
Tillgänglig från: 2016-07-08 Skapad: 2022-11-09Bibliografiskt granskad
Mirsakiyeva, A., Delin, A. & Hugosson, H. W. (2015). Quantum Molecular Dynamics Studies of Thermoelectric Polymer Systems. In: : . Paper presented at 3rd ECCOMAS Young Investigators Conference (YIC), July 20-23, 2015, Aachen.
Öppna denna publikation i ny flik eller fönster >>Quantum Molecular Dynamics Studies of Thermoelectric Polymer Systems
2015 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:hig:diva-40436 (URN)
Konferens
3rd ECCOMAS Young Investigators Conference (YIC), July 20-23, 2015, Aachen
Tillgänglig från: 2022-11-14 Skapad: 2022-11-14 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Smith, A. D., Elgammal, K., Niklaus, F., Delin, A., Fischer, A. C., Vaziri, S., . . . Lemme, M. C. (2015). Resistive graphene humidity sensors with rapid and direct electrical readout. Nanoscale, 7(45), 19099-19109
Öppna denna publikation i ny flik eller fönster >>Resistive graphene humidity sensors with rapid and direct electrical readout
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2015 (Engelska)Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, nr 45, s. 19099-19109Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Royal Society of Chemistry, 2015
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:hig:diva-40431 (URN)10.1039/c5nr06038a (DOI)
Forskningsfinansiär
Kungliga VetenskapsakademienVetenskapsrådet, D0575901Vetenskapsrådet, E0616001Knut och Alice Wallenbergs StiftelseCarl Tryggers stiftelse för vetenskaplig forskning EU, Europeiska forskningsrådet, 277879EU, Europeiska forskningsrådet, 307311Göran Gustafssons stiftelse för naturvetenskaplig och medicinsk forskning (KVA)Stiftelsen för strategisk forskning (SSF)Deutsche Forschungsgemeinschaft (DFG), LE 2440/1-1
Tillgänglig från: 2022-11-14 Skapad: 2022-11-14 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Hugosson, H. W., Cao, W., Seetharaman, S. & Delin, A. (2013). Sulfur- and Oxygen-Induced Alterations of the Iron (001) Surface Magnetism and Work Function: A Theoretical Study. The Journal of Physical Chemistry C, 117(12), 6161-6171
Öppna denna publikation i ny flik eller fönster >>Sulfur- and Oxygen-Induced Alterations of the Iron (001) Surface Magnetism and Work Function: A Theoretical Study
2013 (Engelska)Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 12, s. 6161-6171Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
ACS, 2013
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:hig:diva-40430 (URN)10.1021/jp3102496 (DOI)
Tillgänglig från: 2022-11-14 Skapad: 2022-11-14 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
de Almeida, K. J., Murugan, N. A., Rinkevicius, Z., Hugosson, H. W., Vahtras, O., Ågren, H. & Cesar, A. (2009). Conformations, structural transitions and visible near-infrared absorption spectra of four-, five- and six-coordinated Cu(ii) aqua complexes. Physical Chemistry, Chemical Physics - PCCP, 11(3), 508-519
Öppna denna publikation i ny flik eller fönster >>Conformations, structural transitions and visible near-infrared absorption spectra of four-, five- and six-coordinated Cu(ii) aqua complexes
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2009 (Engelska)Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, nr 3, s. 508-519Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Royal Society of Chemistry, 2009
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:hig:diva-40426 (URN)10.1039/b806423g (DOI)
Tillgänglig från: 2022-11-14 Skapad: 2022-11-14 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Mattesini, M., Ahuja, R., Sa, L., Hugosson, H. W., Johansson, B. & Eriksson, O. (2009). Electronic structure and optical properties of solid C60. Physica. B, Condensed matter, 404(12-13), 1776-1780
Öppna denna publikation i ny flik eller fönster >>Electronic structure and optical properties of solid C60
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2009 (Engelska)Ingår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 404, nr 12-13, s. 1776-1780Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Elsevier, 2009
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:hig:diva-40429 (URN)10.1016/j.physb.2009.02.030 (DOI)
Tillgänglig från: 2022-11-14 Skapad: 2022-11-14 Senast uppdaterad: 2022-11-14Bibliografiskt granskad
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0001-8748-3890

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