高压下KMgF_(3)晶体光学性质的第一性原理研究

Optical properties of KMgF_(3) crystal at high pressure:a first-principles study

本文采用第一性原理的方法, 在100 GPa的压力范围内, 计算了KMgF_(3) 的理想晶体和含空位缺陷晶体的光学性质. 吸收谱数据表明, 在100 GPa范围内, 压力因素不会导致KMgF_(3) 晶体在可见光区有光吸收行为. 钾、镁和氟空位缺陷的存在会使得KMgF_(3) 晶体的吸收边红移 (其中氟空位缺陷引起的红移最显著 ),但这些红移不会导致它在可见光区出现光吸收的现象. 能量损失谱数据显示, 压力因素不仅会使得KMgF_(3) 晶体的能量损失谱有蓝移的行为,而且还会引起它的较强谱峰个数发生变化. 在100 GPa处的缺陷晶体数据指明, 氟空位缺陷会导致其能量损失谱的两个较强谱峰的峰值强度明显降低. 分析表明, KMgF_(3) 晶体有成为冲击窗口材料的可能, 并且本文所获得的结果对未来的实验探究有参考作用.

The optical properties of KMgF_(3) crystal without and with vacancy defects within pressure 100 GPa were calculated by using the first-principles method. The absorptive data show that the pressure factor cannot alter a fact that there is no light- absorption for KMgF_(3) in the visible region within 100 GPa. The potassium, magnesium and fluorine vacancy defects in KMgF_(3) lead to the red-shift of its absorption edge (and the influences of fluorine vacancy defects are the most apparent ), but all these red-shift behaviors do not give rise to its light absorption in the visible region. The loss-function spectrum data in KMgF_(3) indicate that the pressure factor not only causes its blue-shift, but also changes the number of its strong spectrum-peaks. The defective-crystal data at 100 GPa show that the fluorine vacancy defects in KMgF_(3) can cause an obvious reduction in peak-intensity of two strong peaks for its loss-function spectrum. An analysis indicates that KMgF_(3) crystal is likely to be a shock window material, and our results would provide some important information for further experimental study.