Mishra Neeraj, Makov Guy
Department of Materials Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
Materials (Basel). 2022 Aug 31;15(17):6015. doi: 10.3390/ma15176015.
The energetic and mechanical stability of interstitial point defects in binary rock-salt materials were studied using the first-principles method. A novel, stable, and energetically competitive interstitial site (base-interstitial) was identified for anion interstitials in rock-salts. The formation energies of base-interstitial defects were compared with well-explored tetrahedral (body-interstitial) and split interstitials and were found to be energetically highly competitive. For alkali halides and silver bromide, the lowest formation energies are associated with the base-interstitial site and the <110> split interstitial, which are therefore the predominant interstitial sites. However, split interstitials were found to be the energetically preferred configuration in metal monochalcogenide systems. Electronic band structures are affected by the presence of interstitial defects in rock-salt structures. In particular, the Fermi level is shifted below the valence band maxima for the body, base, and split interstitials in metal halides, indicating p-type conductivity. However, the Fermi level remains within the bandgap for metal monochalcogenides, indicating no preferred conductivity for base- and split-interstitial defects. Allowing the defects to be charged changes the relative stability of the interstitial sites. However, the new base-interstitial site remains preferred over a range of potentials for alkali halides. The anion base-interstitial is found to form a triatomic entity with the nearest lattice anions that affect the electronic structure relative to the body interstitial. The discovery of a new interstitial site affects our understanding of defects in binary rock-salts, including structure and dynamics as well as associated thermodynamic and kinetic properties that are interstitial dependent.
采用第一性原理方法研究了二元岩盐材料中间隙点缺陷的能量稳定性和力学稳定性。在岩盐中，为阴离子间隙确定了一种新颖、稳定且能量上具有竞争力的间隙位置（基间隙）。将基间隙缺陷的形成能与已充分研究的四面体间隙（体间隙）和分裂间隙进行了比较，发现其在能量上具有高度竞争力。对于碱金属卤化物和溴化银，最低形成能与基间隙位置和<110>分裂间隙相关，因此这是主要的间隙位置。然而，在金属单硫属化物体系中，发现分裂间隙是能量上更优的构型。岩盐结构中间隙缺陷的存在会影响电子能带结构。特别是，对于金属卤化物中的体间隙、基间隙和分裂间隙，费米能级移动到价带最大值以下，表明具有p型导电性。然而，对于金属单硫属化物，费米能级仍处于带隙内，表明基间隙和分裂间隙缺陷没有优先的导电性。允许缺陷带电会改变间隙位置的相对稳定性。然而，对于碱金属卤化物，在一系列电位范围内，新的基间隙位置仍然是更优的。发现阴离子基间隙与最近的晶格阴离子形成一个三原子实体，相对于体间隙，该实体影响电子结构。新间隙位置的发现影响了我们对二元岩盐中缺陷的理解，包括结构和动力学以及与间隙相关的热力学和动力学性质。
