Correlatedab initiocalculations for ground-state properties of II-VI semiconductors

Abstract

Correlated ab-initio ground-state calculations, using relativistic energy-consistent pseudopotentials, are performed for six II-VI semiconductors. Valence (ns, np) correlations are evaluated using the coupled cluster approach with single and double excitations. An incremental scheme is applied based on correlation contributions of localized bond orbitals and of pairs and triples of such bonds. In view of the high polarity of the bonds in II-VI compounds, we examine both, ionic and covalent embedding schemes for the calculation of individual bond increments. Also, a partitioning of the correlation energy according to local ionic increments is tested. Core-valence (nsp, (n − 1)d) correlation effects are taken into account via a core-polarization potential. Combining the results at the correlated level with corresponding Hartree-Fock data we recover about 94% of the experimental cohesive energies; lattice constants are accurate to ∼1%; bulk moduli are on average 10% too large compared with experiment.

Tight‐binding molecular dynamics simulation of ZnSe liquid within the local environment dependence

“…The cinnabar structure is found to be an intermediate phase between the ZB and the RS structures of ZnSe, a behavior which was previously associated only with the Te and Hg based II-VI compounds. [42] The structural parameters of the cinnabar form of ZnSe have very similar behavior as those found in Ref. 41.…”

The method of increments—a wavefunction-based ab initio correlation method for solids

“…For the correlation calculation we have chosen a basis set of vtz quality with a 2d1f polarisation basis set (for details see Refs. [39,42,41]). With this basis set we calculate approximately 82% of the correlation contributions to the cohesive energies.…”

“…The critical cases are substances with intermediate binding character like the II-VI semiconductors where a charge transfer of about one electron occurs or transition metal oxides like rutile (TiO 2 ), where the oxygen atom is not charged fully 2-. For the series ZnS, ZnSe and ZnTe of II-VI semiconductors, where the ionicity decreases and the delocalisation of the bonds increases, we tested and compared different embedding [42]: We have checked the simple embedding with hydrogen atoms only (X 4 Y 4 H 18 clusters); a more sophisticated embedding with a shell of Zn and chalconide atoms in a minimal basis set, where only the outer shell is saturated with hydrogen atoms resulting in a X 13 Y 13 H 30 cluster; finally an embedding with point charges. In the latter embedding one shell of Zn-atoms with a minimal valence basis [1s1p] is added in the surrounding of the negatively charged ions to allow the electrons to delocalise and hybridise with the neighbours as it occurs in the real solid.…”

“…But of course a combination of the method of increments with the local correlation method of Pulay is possible to reduce the computational effort even further [31,32]. The focus of this review lies on the method of increments and its application to ground-state properties of various material classes: From insulators [33][34][35][36][37] over semiconductors [20,21,[38][39][40][41][42] to metals [22,43,44], from strongly bound ionic or covalent systems to weakly bound van der Waals solids [45][46][47], from large molecules [31,48] over polymers [49][50][51][52][53][54][55][56] to three-dimensional solids, from weakly correlated systems to strongly correlated ones such as transition-metal oxides [57,58] and rare-earth nitrides and oxides [59][60][61]. The generalisation to metals is discussed for the example of solid mercury [44,62] and the inclusion of multi-reference treatments for strongly correlated systems is presented for a one-dimensional lithium chain [43].…”

Electronic structure of crystalline binary and ternaryCd−Te−Ocompounds

“…Although there are many reports of ab-initio calculations of Cd and Te compounds, including c-CdTe, 20,21,22,23 l-CdTe, 24 c-CdO 22,25,26,27,28,29 and TeO n clusters 30,31,32,33,34,35,36 , the crystalline TeO 2 and the ternary compounds remain largely unexplored. Only one ab-initio study of a CdTe-O system, which addresses the O adsorption on CdTe surfaces, is known to the authors.…”