Electronic structure of (SN)xand its intercalate (SNBry)x

Abstract

A first-principles self-consistent calculation of the energy band structure of (SN)x has been made by using the numerical-basis-set LCAO method. The resulting Fermi surface consists of two electron and two hole pockets which have the shapes of flattened tubes or flattened ellipsoids. The calculated density of states agrees well with both the X-ray photoemission spectroscopy (XPS) data and the Fermi level density of states obtained from the specific heat measurement. On the basis of the band-structure results, the calculation of the imaginary part of the dielectric function of (SN)x is carried out. The characteristic features of the observed optical absorption spectra of (SN)x are satisfactorily explained by the theoretical results. Moreover, the Fermi surface of (SNBry)x is calculated in terms of a rigid band model based on the present self-consistent band structure of (SN)x. The resulting Fermi surface of (SNBry)x, together with that of (SN)x, clarifies the origin of the observed characteristic change of the physical properties of (SN)x upon bromination.