用第一性原理研究K空位对KDP晶体激光损伤的影响

 用基于密度泛函理论及超软赝势的第一性原理研究了KH­­­₂PO₄(KDP)晶体中K空位的电子结构、形成能及驰豫构型。讨论了K空位形成后电荷密度的重新分布、相应的电子态密度和能带结构等性质。计算得到中性K空位的形成能为6.5 eV, 远小于间隙K原子点缺陷形成能13.07 eV。K空位的存在使晶胞体积增大, 分别沿结晶学轴a方向增大近0.8%, b方向增大近0.87%, c方向增大近1.2%，同时使与之配位的8个氧原子发生较大位移，使这8个氧形成的空腔体积增大近3.2%。空腔体积的增大不仅促进了各种点缺陷的扩散迁移，而且有利于其它杂质原子的填隙。K原子迁移率的增大会引起离子电导率的增大，因而会降低KDP的激光损伤阈值，因此从这个方面讲，K空位的存在是不利的。但是如果能从实验上（如热退火）利用K空位所造成的扩散通道排出或改善缺陷结构，则可提高KDP晶体的光学质量。

First-principle studies of the effects of K vacancy in KDP crystals upon laser-induced damage

This paper presents the ab initio calculations results of K vacancy in KDP crystals.The electronic structures and formation energy as well as the relaxing configuration of K vacancy were detailedly studied.The properties of density of states and band structure on KDP with K vacancy were discussed.The formation energy of K vacancy was calculated to be about 6.5 eV and much lower than that of K interstitial(13.07 eV).The cell parameters increase due to K vacancy and the volume enlargement of cavum surrounded by the neighboring eight O atoms is nearly 3.2%,which is in favor of the transference for K atoms and is benefit for the impurity atoms to fill the cavum in KDP.The increasing of mobility ratio of K induces the increasing of ionic conductivity,therefore laser-induced damage threshold will be decreased.