A Pseudopotential Approach to the Structure of As

Abstract

The internal energy of As crystal is investigated as a function of structure parameters and volume in terms of the pseudopotential expansion method. An atomic model potential derived from Lin and Falicov's one is used. Calculations in second order approximation explain successfully the stability of the unusual A7 structure of As, the temperature dependence of structure parameters, and pressure-induced phase transformation from A7 to simple cubic, but give rise to unusual results in conflict with experimental facts with respect to large volume change. The third order contribution does not improve the situation. It is discussed that these shortcomings are attributed to the truncated nature of Lin-Falicov's potential.