有限温度Si_xGe_(1-x)合金介电函数第一性原理模拟

First-principles Study on Finite Temperature Dielectric Function of Si_xGe_(1-x) Alloy

基础辐射物性介电函数在热辐射研究中扮演了重要的角色。通过运用第一性原理分子动力学(AIMD)方法研究了Si_xGe_(1-x)合金的介电函数随温度变化的规律。以热平衡构型作为输入结构,AIMD方法可有效计算不同温度下固体材料的电子能带结构,进而得到介电函数。研究表明,在300 K温度下Si_xGe_(1-x)合金介电函数的理论计算值与对应的实验结果吻合;且随着合金中Si/Ge比例的增加,合金的禁带宽度增大,介电函数虚部主峰位置红移且幅值增强。

The fundamental thermophysical parameter dielectric function plays a significant role in thermal radiative research.The temperature dependence of dielectric function of Si_xGe_(1-x)alloys is studied with the first-principles molecular dynamics(AIMD) method.Choosing thermally balanced configurations as input structure for first-principles calculations,the AIMD approach can naturally include temperature effect into computing electronic band structure and dielectric function of solids.The calculated results of room-temperature dielectric function of Si_xGe_(1-x) alloy demonstrate good agreement with experimental data.Moreover,as the ratio of Si/Ge increases,the energy gap of the alloy enlarges,the dominant peak of dielectric function shifts to lower energy and the amplitude damps.