KDP晶体中铝取代钾点缺陷第一性原理计算

First Principles Calculation on Point Defect of Al Substituting for K in KDP Crystals

为了明确Al3+在KDP晶体生长过程中对光学性质和力学性质的具体影响,采用第一性原理计算程序包VASP软件计算并分析了Al取代K对KDP晶体的晶体结构、电子能态密度和光学性质,并同理想KDP晶体进行对比研究。结果表明,KDP晶体中Al取代K的缺陷形成能为0.974 e V,并且Al替位K点缺陷引起的晶格畸变非常微弱,缺陷比较容易形成。Al取代K后晶体能带中价带顶附近的态密度发生了变化,并且带隙中存在缺陷能级,取代后KDP晶体的带隙宽度减小为4.37 e V,缺陷增加了KDP晶体对可见到紫外波段的光子吸收,影响KDP晶体光学质量及其激光损伤性能。计算力学性质发现,Al替位掺杂KDP晶体比理想KDP晶体的杨氏模量增加了,这会减弱晶体抗激光损伤能力。

To illustrate how Al3 ＋ion affects optic properties during KDP crystals growth,the first-principle package VASP is used to calculate the structure of KDP crystals,electronic state density and optical properties of KDP in which K is replaced with Al. Defect formation energy is about 0. 974 e V and the introduction of Al causes little lattice distortion,which shows that the defect is easy to form. That an Al atom substitutes for a K atom in KDP crystals results in the variation of band near the top of the valence band. Defect levels were observed in the band gap of pure KDP crystals,and the band gap of such defect crystal is reduced to 4. 37 e V. Hence,the increasing of the absorption of photons of visible and ultraviolet light can affect the optical quality and laser damage performance. By calculating the mechanical properties of KDP crystals,it is found that the Young＇s modulus of Al-substituted KDP crystals are larger than that of pure KDP crystals,which is also not good for the laser damage resistance of KDP crystals.