高压相BeO晶体的电子结构和光学性质

应用基于密度泛函理论的第一性原理研究方法,考虑广义梯度近似(GGA)下的交换关联势,模拟计算了高压下纤维锌矿(WZ)、闪锌矿(ZB)和岩盐(RS)结构氧化铍(BeO)晶体的电子结构和光学性质等.计算结果表明,随着压力的增加,同种结构下原子间的键长和电荷转移有所减小,并且价带和导带分别向低能和高能方向移动,禁带展宽.与常压下的BeO相比,随着压力的增加,三种结构的BeO晶体的光学性质有一定的变化,介电函数、吸收系数、折射率以及电子能量损失谱曲线出现更多的精细结构,峰的数量增多;各高压相结构的吸收谱和能量损失谱宽度逐次展宽;吸收系数曲线的吸收峰及其位于低能区域的吸收边以及电子能量损失谱峰的位置均发生一定程度的蓝移.

Electronic Structures and Optical Properties of BeO under High Pressure

Density functional theory within the generalized gradient approximation (GGA) was used to investigate the electronic structures and optical properties of the BeO crystal in wurtzite (WZ), zinc blende (ZB), and rocksalt (RS) phases under high pressure. Results indicated that with an increase in pressure for all three structures, the BeO bond became shorter, the charge transfer decreased, the conduction band shifted to higher energy and consequently the width of bandgap became wider. Compared to BeO at 0 GPa, the curves of the dielectric functions, absorption coefficients, and electron energy-loss functions of the three high pressure phases showed finer structures. With an increase in pressure, the absorption coefficient spectra and the energy-loss functions expanded while the absorption edges and the absorption peaks of the absorption curves as well as the peaks of the energy-loss functions showed a blue shift to some extent.