Enhanced static approximation to the electron self-energy operator for efficient calculation of quasiparticle energies
Enhanced static approximation to the electron self-energy operator for efficient calculation of quasiparticle energies
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DOI：
10.1103/physrevb.82.195108
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发表时间：
2010-11-09
影响因子：
3.7
通讯作者：
Hybertsen, Mark S.
中科院分区：
文献类型：
--
作者：
Kang, Wei;Hybertsen, Mark S.
为了有效地计算准粒子能量，提出了一种改进的电子自能算符的静态近似。对Hedin提出的静态库仑-空穴屏蔽交换(COHSEX)近似的分析表明，大部分误差来自于假定的库仑空穴绝热积累的短波贡献。一个与波矢有关的修正因子可以作为新的静态近似的基础。这个因子可以用一个单一的标度函数来近似，该标度函数是由均匀的电子气模型确定的。用一种基于对称性考虑的简单ANSAZ方法来捕捉真实材料中的局域场效应。由于继承了COHSEX近似，新的近似给出了厄米自能算符，并且空态上的求和从自能算符的计算中去掉了。对晶体、分子、原子和碳纳米管等不同材料进行了测试，将新的近似计算与GW计算进行了比较。最小间隙的精度约为10%或更高。像在COHSEX近似中一样，占用的带宽被高估了。
An enhanced static approximation for the electron self-energy operator is proposed for efficient calculation of quasiparticle energies. Analysis of the static Coulomb-hole screened-exchange (COHSEX) approximation originally proposed by Hedin shows that most of the error derives from the short-wavelength contributions of the assumed adiabatic accumulation of the Coulomb hole. A wave-vector-dependent correction factor can be incorporated as the basis for a new static approximation. This factor can be approximated by a single scaling function, determined from the homogeneous electron-gas model. The local field effect in real materials is captured by a simple ansatz based on symmetry consideration. As inherited from the COHSEX approximation, the new approximation presents a Hermitian self-energy operator and the summation over empty states is eliminated from the evaluation of the self-energy operator. Tests were conducted comparing the new approximation to GW calculations for diverse materials ranging from crystals, molecules, atoms and a carbon nanotube. The accuracy for the minimum gap is about 10% or better. Like in the COHSEX approximation, the occupied bandwidth is overestimated.