The Heyd-Scuseria-Ernzerhof (HSE) screened hybrid density functional has been proven to yield lattice constants and energy gaps of semiconductors in better agreement with experiment than standard local semilocal exchange correlation functionals. latter underestimate the band many severely, i.e., case ZnO underestimation amounts 75% experimental value. In this work, we report on structure optimization study electronic gap wurtzite phase performed within density-functional theory using...

Different stacking sequences of graphene are investigated using a combination experimental and theoretical methods. The high-resolution transmission electron microscopy (HRTEM) the sequence several layers graphene, formed on C-terminated 4H-SiC(0001) surface, was used to determine interlayer distances. These data prove that three metastable configurations exist: ABAB, AAAA, ABCA. In accordance these, findings those cases were considered theoretically, Density Functional Theory calculations...

In this study, the fundamental properties of spontaneous and piezo polarization surface polarity were defined. It was demonstrated that Landau definition as a dipole density could be used in infinite systems. Differences between bulk distinguished, thus creating clear identification both components. This is agreement with numerous experimental data-red shift presence absence for wurtzite zinc blende multiquantum wells (MQWs), respectively. A local model created to calculate electric density....

The crystal structure of arsenolite, the cubic polymorph molecular arsenic(III) oxide, has been determined by single-crystal X-ray diffraction up to 30 GPa. bulk is monotonically compressed with no detectable anomalies 60% initial volume at experimental As4O6 compression exceeds that obtained various theoretical models within density functional theory framework. molecules are deformed toward a more tetrahedral shape. A surprising property arsenolite immersed in helium revealed above 3 GPa;...

The technology of GaN is very advanced due to excellent figures merit relevant for key applications like LEDs or high-power–high-frequency transistors. Nevertheless, some fundamental physical properties, including the phase diagram, this so important semiconductor, are still not determined. In work, simulations crystal behavior at heating extremely high temperatures in a wide pressure range reported. Ab initio density functional theory (DFT) molecular dynamics extensive calculations were...

The principal structural defects in graphene layers, synthesized on a carbon-terminated face, i.e., the SiC(000$\overline{1}$) face of $4H$-SiC substrate, are investigated using microscopic methods. Results high-resolution transmission electron microscopy (HRTEM) reveal their atomic arrangement. mechanism such defects' creation, directly related to underlying crystallographic structure SiC is proposed. connection between $4H$-SiC(000$\overline{1}$) surface morphology, including presence...

Electric field, uniform within the slab, emerging due to Fermi level pinning at its both sides is analyzed using DFT simulations of SiC surface slabs different thickness. It shown that for thicker slab field nonuniform and this fact related state charge. Using electron density potential profiles it proved high precision necessary take into account enough number Si-C layers. We show 12 diatomic layers leads satisfactory results. also demonstrated change opposite side termination, by type...

An original room-temperature and ambient-pressure method of claudetite II crystallization consisting in ammonium arsenate(III) decomposition is presented. Claudetite characterized by single crystal powder X-ray diffraction, Raman spectroscopy differential scanning calorimetry. I equations state were obtained DFT calculations their energies incorporating dispersive contribution accounted for the Grimme method. It has been shown that metastable investigated pressure range a new high-pressure...

Ab initio calculations are used to determine the basic physical properties of hydrogen adsorption at N-terminated GaN(0001̅) surface. It was shown that Fermi level is pinned valence band maximum (VBM) for coverage θH = 0.75 ML above which shifted conduction minimum (CBM). Application electron counting rule (ECR) indicates ML, not pinned, located in bandgap. confirmed energy depends on surface as predicted and explained earlier (Krukowski et al. J. Appl. Phys. 2013, 114, 143705 Krukowski 115,...

Ab initio density functional theory simulations were used to investigate the influence of hydrogen intercalation on electronic properties single and multiple graphene layers deposited SiC(0001) surface (Si-face). It is shown that carbon layer, known as a buffer covalently bound SiC substrate, liberated after intercalation, showing characteristic Dirac cones in band structure. This agreement with results angle resolved photoelectron spectroscopy measurements SiC-graphene samples. In contrast...

Abstract The first principles calculations by using the plane‐wave pseudopotential method in scheme of density functional theory were performed for polymorphs ZnO: wurzite‐, zinc‐blende‐, rocksalt‐structures, and yet experimentally undiscovered CsCl‐structure. elastic behavior stability structures are investigated compared to experimental data, where available. For each structure, electronic properties calculated within LDA+U approximation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A vertical electrical conductivity of an ultrawide bandgap AlGaN p–n junction with Al-composition-graded AlxGa1−xN (0.45 ≤ x) p-type layer was systematically investigated via experiments and numerical simulation. The experimental results revealed that the initial Al composition should be sufficiently high without Mg dopants to generate enough holes by polarization-induced doping even though is higher than conventional bulk p-AlGaN. mechanism behind conduction simulation, which shows...

Abstract The electronic structure of C60 molecules with carbon substituted by other elements such as boron or nitrogen has been calculated for in the singlet state even number electrons. Therefore, case and substituents, calculations have performed ionized molecules. results obtained from our density functional prove than C60-x-yBxNy both HOMO LUMO levels are split due to lower symmetry molecule Influence deformation on states, which is interesting because fullerenes may undergo solvate...

We report ab initio plane wave density functional theory studies of thermodynamic properties isolated cation substitutions and oxygen vacancies in magnesium spinel, $\mathrm{Mg}{\mathrm{Al}}_{2}{\mathrm{O}}_{4}$. The formation enthalpy Ca, Cu, Zn Mg indicate that transition metal dopants are energetically stable the bulk $\mathrm{Mg}{\mathrm{Al}}_{2}{\mathrm{O}}_{4}$ at low chemical potential. electronic defects ternary spinel show close similarities with those binary oxides; MgO...

Density functional study has been performed for a group of compounds derived from sulphur hexafluoride (SF6) by consecutively substituting fluorine with hydrogen. SF6 is widely used as the insulating gas in electrical industry and recognised one greenhouse gases extraordinary global warming potential. The aim present to look potential industrial alternatives well examine mechanisms that can contribute its faster atmospheric decay. ground state geometries, binding energies, vibrational...

A nonradiative recombination channel is proposed, which does not vanish at low temperatures. Defect-mediated recombination, known as Shockley–Read–Hall (SRH) reformulated to accommodate Coulomb attraction between the charged deep defect and approaching free carrier. It demonstrated that this effect may cause a considerable increase in carrier velocity center. The considerably increases capture rates. that, typical semiconductor device or medium, SRH rate temperatures much higher cannot be...

Ab initio self-consistent all-electron spin-polarized calculations were performed for the ground state and several low-lying states of CoO molecule using local-spin-density approximation. The calculated energies spectroscopic constants are generally in reasonable agreement with experimental data. Contrary to previous theoretical reports, was found be $^{4}\mathrm{\ensuremath{\Sigma}}^{\mathrm{\ensuremath{-}}}$ lowest-lying excited state, $^{4}\mathrm{\ensuremath{\Delta}}$, at 0.49 eV above...

Density-functional calculations of adsorption the F− and OH− ions on TiO2 anatase (101) surface have been performed. Changes to electronic properties prior after investigated. The most profound change in structure is diminishing band gap system. While for pure (without adsorbents) 1.77 eV wide, modified with widths equal 0.35 0.39 eV, respectively. That means, excitation energy over four times smaller than case Nevertheless, all cases studied maintains its semiconducting properties.