Gao Xing, Daw Murray S
Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA.
J Phys Condens Matter. 2009 Jan 28;21(4):045401. doi: 10.1088/0953-8984/21/4/045401. Epub 2008 Dec 15.
We have studied by the first-principles total energy method the off-center instability of a substitutional Li impurity in KCl. We report here the results of super-cell calculations of the energy associated with displacing the Li along [Formula: see text], [Formula: see text] and [Formula: see text] directions relative to the K vacancy. To understand the influence of relaxations, we performed three levels of relaxations-only first nearest neighbors of the vacancy, first and second nearest neighbors, and full relaxation. Our calculations show that the relaxation significantly affects the energy surface and that the relaxation of the nearest neighbors to the vacancy accounts for most of the trend. The position of minimum energy for the Li was found to be along the [Formula: see text] direction. The calculated well along [Formula: see text] is 102 meV deep relative to the on-center energy and lies about 0.86 Å off-center. Minima along adjacent [Formula: see text] directions are separated by a saddle-point barrier of 44 meV along the [Formula: see text] direction. Our calculated results are in agreement with prior model calculations and we believe our calculated potential surfaces are the best theoretical result so far.
我们采用第一性原理总能量方法研究了KCl中替代型锂杂质的偏离中心不稳定性。在此，我们报告了与锂相对于钾空位沿[公式：见正文]、[公式：见正文]和[公式：见正文]方向位移相关的能量的超胞计算结果。为了理解弛豫的影响，我们进行了三个层次的弛豫——仅空位的第一近邻、第一和第二近邻以及完全弛豫。我们的计算表明，弛豫显著影响能量表面，且空位最近邻的弛豫占了大部分趋势。发现锂的最低能量位置沿[公式：见正文]方向。相对于中心能量，沿[公式：见正文]计算出的阱深为102毫电子伏，且偏离中心约0.86埃。沿相邻[公式：见正文]方向的最小值被沿[公式：见正文]方向44毫电子伏的鞍点势垒隔开。我们的计算结果与先前的模型计算结果一致，并且我们相信我们计算出的势能面是迄今为止最好的理论结果。
