Theoretical studies of cation sublattice ordering in AgSbTe2 and AgSbSe2 - Electron density topology and bonding properties

Specific order in cation sublattice of AgSbX2 chalcogenides is an important factor influencing their electronic structure and thus thermoelectric properties. For several selected ordering configurations specified for AgSbX2 chalcogenides (X = Te, Se) ab initio calculations were carried out. Relationship between local order and cohesive energy is discussed and most preferable systems are indicated. Detailed analysis of electron density topology is presented, and Brown's Bond Valence Model is employed in parallel in order to explain elementary features of cation sublattice arrangement in these compounds. Electronic structure properties of chosen configurations are analysed and densities of states are used to indicate relationship between structure ordering and thermoelectric properties of AgSbX2 materials. It is shown that two most stable configurations of Ag/Sb ordering are practically identical from local interactions viewpoint and should be treated as equivalent. (C) 2017 Elsevier B.V. All rights reserved.