γ-B_(28)光学性质的第一性原理研究

First-principles Calculations for Optical Properties of γ-B_(28)

利用基于密度泛函第一性原理的GGA方法,计算研究了硼的高压相γ-B28的能带结构、态密度、分态密度和光学性质。计算结果表明,γ-B28具有半导体能带结构的特征,其带隙达1.619eV,且整个带结构由杂化的硼2p态和2s态组成,且2p态占主导地位。γ-B28的静态介电常数为11.0733,静态的折射率为3.328,介电函数虚部的吸收边位于1.7eV左右,同时,在2.693eV和5.232eV处有2个明显的特征峰。γ-B28的反射系数在0～16eV范围内随着能量的升高而逐渐增大,但在19.4eV时反射系数急剧下降,而吸收系数的数量级达105cm-1,其电子能量损失谱(EELS)的共振峰在19.4eV处,与反射系数的陡降相对应。

First-principles calculations are carried out to investigate the band structure, density of states and optical properties of γ-B28, using the method of the generalized gradient approximation （GGA） based on density func- tional theory. The band structure of 7-B28 indicates it is a kind of semi-conducting material with wide-band gap of 1. 619eV, and the band structure is hybrid by 2p and 2s electron. The static dielectric constant is 11. 0733, the static refractive index is 3. 328. The absorption starts of the imaginary part of dielectric constant is about 1.7eV, and there are two obvious characteristic peaks at 2. 693eV and 5. 232eV. The reflection index of γ-B28 increases with energy improved at 0-16eV, but there is an abrupt reduction at 19.4eV, which corresponding to the peak of EELS. The ab- sorption coefficient is as large as 105 cm-1 , and the absorption is mainly localized in the low energy region.