Kubo-Greenwood公式在分子模拟中的推广
An extension of the Kubo-Greenwood formula for use in molecular simulations
摘要：
本文讨论了广泛应用的Kubo-Greenwood公式（KGF）的基础，并扩展了它的适用范围。电导率是从电流密度中推导出来的，并且只使用了概率幅度而不是跃迁概率。结果表明，简并态在低频或零频外电场中对电导率的贡献以及简并态在有限频率外电场中对电导率的贡献都是有限的.改进后的电导率表达式不包括常见的“能量守恒”δ函数，也不需要人为加宽δ函数的参数来限制直流极限。我们探讨了两种计算电流密度的方法。我们讨论了多电子统计在计算单粒子近似电导率中的作用，并表明传统的KGF是由于单粒子激发态的贡献。
英文摘要：
We discuss the foundations and extend the range of applicability of the widely used Kubo-Greenwood formula (KGF) for the electronic conductivity. The conductivity is derived from the current density, and only the probability amplitude rather than the transition probability is used. It is shown that the contribution to the conductivity from degenerate states in a low or zero frequency external electric field and the contribution from states near resonance with a finite frequency external field are finite. The improved conductivity expression does not include the familiar "energy conserving" delta function, and no artificial broadening parameter for delta function is required for the DC limit. We explored two methods of computing current density. We discuss the role of many-electron statistics in computing the conductivity in single-particle approximations, and we show that the conventional KGF is due to the contribution from single-particle excited states.
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