高压下BaF_(2)光学性质的模拟计算

High-pressure optical properties of BaF_(2) crystal via first-principles simulations

探寻新的冲击窗口材料是高压科学领域中的一个重要课题.为此,在100 GPa范围内,通过第一性原理方法计算了BaF_(2)晶体的吸收谱以及在532 nm处的折射率.结果表明:(1)压力和结构相变因素不会引起BaF_(2)晶体在可见光区域出现光吸收;氟和钡空位点缺陷的存在将使得BaF_(2)吸收谱的吸收边红移,但这些红移行为不会导致该材料在可见光区域内出现光吸收的现象,由此可以初步推测,BaF_(2)晶体有成为冲击窗口材料的可能.(2)BaF_(2)的折射率在其三个结构相区都随压力的增大而增大,并且BaF_(2)的高压相变也使得其折射率升高;钡空位点缺陷的存在将导致其折射率减小,而氟空位点缺陷却引起其折射率增加.

Exploring new shock window-materials is an important issue in high-pressure science.The first-principles simulative calculations for the BaF_(2)absorption spectra and refractive indexes at 532 nm within 100 GPa show that:(1)pressures and structural transitions cannot cause its light-absorption in the visible district.(2)The barium and fluorine vacancy defects in BaF_(2)result in the red-shift of its absorption edge(the effects of fluorine vacancy defects are the more apparent),but all these red-shift behaviors do not yield its light absorption in the visible district.So,it can be preliminarily inferred that BaF_(2)crystal is probable to be a shock window material.(3)In BaF_(2)three structural phase districts,the refractive-index increases with increasing pressure.Moreover,the high-pressure structural transitions in BaF_(2)also result in an increase in its refractive index.The barium vacancy defect decreases the BaF_(2)refractive index,but the fluorine vacancy defects increase its refractive index.