Atomic arrangement in the mSnTe-nBi2Te3 compounds by electronic structure calculations

Abstract

mAIVTe-nB2VTe3 systems form well-defined compounds, characterized by a layer structure, where the Te planes are intercalated by the metallic ones. Both ordered and random distributions of A and B atoms in the cation sites have been invoked by the experimentalists. The different possible sequences of filled and unfilled sandwiches of Te planes might induce additional disorder in the unit cell when n>1. The authors' calculations for such a system, specifically for mSnTe-nBi2Te3, based on a tight-binding effective Hamiltonian, give a clear indication in favour of ordered structures. This would explain why these systems do not form solid solutions. The results for the sequence of Te and metallic planes suggest SnBi2Te4 to be the only stable compound in the system, the others quoted in the literature being just combinations of that unit cell with the Bi2Te3 cell.