Temperature and composition dependence of short-range order and entropy, and statistics of bond length: the semiconductor alloy (GaN)_(1-x)(ZnO)_x

摘要

We present total energy and force calculations for the (GaN)_(1-x) (ZnO)_x alloy. Siteoccupancy configurations are generated from Monte Carlo (MC) simulations, on the basis of a cluster expansion model proposed in a previous study. Local atomic coordinate relaxations of surprisingly large magnitude are found via densityfunctional calculations using a 432-atom periodic supercell, for three representative configurations at x =0:5. These are used to generate bondlength distributions. The configurationally averaged compositionand temperaturedependent shortrange order (SRO) parameters of the alloys are discussed. The entropy is approximated in terms of pair distribution statistics and thus related to SRO parameters. This approximate entropy is compared with accurate numerical values from MC simulations. An empirical model for the dependence of the bond length on the local chemical environments is proposed.