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 on the(GaN)$_{1-x}$(ZnO)$_{x}$ alloy. Site-occupancy configurations are generated byMonte Carlo (MC) simulations, based on a cluster expansion (CE) model proposedin a previous study. Surprisingly large local atomic coordinate relaxations arefound by density-functional calculations using a 432-atom periodic supercell,for three representative configurations at $x=0.5$. These are used to generatebond length distributions. The configurationally averaged composition- andtemperature-dependent short-range order (SRO) parameters of the alloys arediscussed. Entropy is approximated in terms of pair distribution statistics andthus related to SRO parameters. This approximate entropy is compared withaccurate numerical values from MC. An empirical model for the dependence ofbond length on local chemical environments is proposed.