P. Krusius

Band structure of group IVA transition-metal dichalcogenides

A systematic study of the electronic properties of the layered group IVA transition-metal dichalcogenides TiS2,, TiSe2, ZrS2 ZrSe2 has been performed using the ab initio fully self-consistent symmetrised OPW method according to the local density formalism (Xalpha exchange correlation). Core states, energy bands and valence densities of states are presented. The valence eigenstates are analysed in terms of Slater-Koster LCAO interpolation models. A general discussion of properties and trends in the family of group IVA transition-metal dichalcogenides also includes HfS2 and HfSe2.

The self-consistent electronic spectrum of the layer crystal TiS2

The self-consistent OPW method has been applied to investigate the electronic spectrum of the ideal 1T phase of TiS2. Both valence and core state energies are presented. Bonding properties are discussed in terms of the self-consistent charge densities. Exchange-correlation effects and crystal parameter refinements are shown to have a minor influence on the optical gap of about 1 eV. It is concluded that the electronic properties of real TiS2 crystals in the neighbourhood of the Fermi level do not seem to be determined by properties of the 1T phase alone.

The electronic ground state of the layer compoundsZrS2, TiS2 andTiSe2

SummaryThe band structures of the transition metal layer compounds ZrS2, TiS2 and TiSe2 in the 1T-phase have been determined by means of the symmetrized self-consistent OPW method. No additional constraints are set on the effective crystal potential. Energy spectra and valence charge densities are discussed. In addition, conclusions on the layer-layer interaction are drawn.RiassuntoSi sono determinate le strutture di banda dei composti a strati dei metalli di transizione ZrS2, TiS2 e TiSe2 nella fase 1T usando il metodo OPW simmetrizzato autoconsistente. Non si sono poste ulteriori condizioni al potenziale efficace del cristallo. Si sono discussi gli spettri di energia e le densità di carica di valenza. Inoltre si traggono conclusioni sull’interazione strato-strato.РезюмеОпределяется зонная структура слоистых соединений переходных металлов ZrS2, TiS2 и TiSe2 в 1T-фазе, используя симметризованный самосогла-сованный метод ортогонализованных плоских волн. На эффективный кристал-лический потенциал не накладывается никаких ограничений. Обсуждаются энер-гетические спектры и плотности валентных зарядов. Кроме того, делаются выводы о характере взаимодействия между слоями.

Charge density of group IVA transition-metal dichalcogenides

A systematic study of electronic properties of the layered group IVA transition-metal dichalcogenides TiS2, TiSe2, ZrS2 and ZrSe2 has been performed using the fully self-consistent OPW method according to the local density formalism. The X-ray form factors and the charge density are presented. The anisotropy, the bonding properties and the layer-layer interaction are analysed and discussed in detail. Also a general conclusion on the electronic properties of the group IVA transition-metal dichalcogenides is given.

Self-Consistent Valence Charge Density of the 1T Layer Compounds TiS2, TiSe2, ZrS2 and ZrSe2

A systematic presentation of the valence charge densities for TiS2, TiSe2, ZrS2 and ZrSe2 is given in the form of contour maps. The effects of the variation of the Xα constant α and the layer height parameter are studied. The bonding mechanism is also discussed. The more metallic nature of the valence charge density of TiSe2 in the hexagonal metal plane, as compared with the other materials, is in agreement with the 2a × 2a × 2c supercell formation.

The overlap matrix and the Slater-Koster interpolation scheme

Abstract The usual assumption of a unit overlap matrix in the LCAO interpolation scheme of Slater and Koster leads to an inconsistency, which is discussed in general terms and demonstrated for the layered 1T-polytype of the semiconductor ZrS 2 .

Self-consistent Ground State of Trigonal Tellurium

The purpose of the present paper is to report our non-relativistic Xα calculations of trigonal Te. In the self-consistent (SC) symmetrized OPW (SOPW) method used [1] both the valence states represented by SOPWs and the core states are included in the SC iteration. The only parameters entering into our calculations are the lattice constants a=0.44572 nm, u=0.11736 nm, c=0.5929 nm and the Xα-parameter α. Our SC α=1 band structure is quite similar to the SC pseudopotential one [2], Our bands are characteristically ∼0.2 eV broader and the gaps about the same amount narrower. Our rough α=2/3 density of states (DOS) histogram has two s, two p-bonding and one broader p-non-bonding peaks in agreement with earlier experience [2,4,5].

OPW Band Structure of Layered TiS2

An empirically refined OPW band structure has been determined for the layered transition metal dichalcogenide TiS2. The over-all energy gap has been adjusted approximately to the traditional value of Wilson and Yoffe but in addition a preliminary self-consistent OPW calculation is used to test the relevance of the adjusting procedure. Density of states and optical properties are briefly discussed with reference to the determined band structure.