Abstract:
The electronic band structure and charge densities for two transition metal monosulfides TiS and VS, with the NiAs-type structure have been calculated using the band theoretical Green's function technique. The results of these calculations are interpreted in terms of chemical bonding and stabilization effects in the solid. It is found that the charge density of the transition metal d -like electrons is maximized in the direction through centers of triangular faces of the octahedraUy coordinated sulfur atoms, rather than along the c axis between adjacent metal atom layers, a distribution which was originally believed to stabilize the NiAs-type structure.
http://scitation.aip.org.sci-hub.cc/content/aip/journal/jcp/76/8/10.1063/1.443482
INTRODUCTION
It has been well established by the work of a number of investigators [recently reviewed in Ref. (1)] that TiS crystallizes in the NiAs-type structure and stoichiometric VS undergoes a second-order phase transition from MnP-type to NiAs-type at about 575°C. The electronic structures of these solids are of interest in part because of a desire to understand the electronic interactions stabilizing the NiAs-type structure relative to, for example, the NaCI-type and WC-type structures. These electronic structures were recently discussed by Goodenough. 2 One of the structural features that makes the comparison of TiS and VS particularly interesting is the anomalously large c axis of TiS(c/a = 1. 93 compared with 1. 76 for VS and 1. 63 for hypothetical close-packed hard sphere anions). Another interesting feature is the charge density wave instability in VS3 that results in distortion to the MnP-type structure discussed by Liu et al.
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