We theoretically investigate defect formation energies in LaOXS2 (X=Sb, Bi) using first-principles calculation. We find that the oxygen vacancy is relatively stable, where its formation energy is higher in X= Sb than in X= Bi. An interesting feature of X= Sb is that the vacancy of the in-plane sulfur atom becomes more stable than in X= Bi, caused by the formation of an Sb2 dimer and the electron occupation of the impurity energy levels. The formation energies of cation defects and anion-cation antisite defects are positive for the chemical equilibrium condition used in this study. Fluorine likely replaces oxygen, and its defect formation energy is negative for both X= Sb and Bi, while that for X= Sb is much higher than X= Bi. Our study clarifies the stability of several point defects and suggests that the in-plane structural instability is enhanced in X= Sb, which seems to affect a structural change caused by some in-plane point defects.
@article{arxiv.2110.12593,
title = {First-principles study of defect formation energies in LaO$X$S$_2$ ($X=$ Sb, Bi)},
author = {Masayuki Ochi and Kazuhiko Kuroki},
journal= {arXiv preprint arXiv:2110.12593},
year = {2022}
}