Jha Punit K, Hirata So
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Phys Rev E. 2020 Feb;101(2-1):022106. doi: 10.1103/PhysRevE.101.022106.
Benchmark data are presented for the zeroth- through third-order many-body perturbation corrections to the electronic Helmholtz energy, internal energy, and entropy in the canonical ensemble in a wide range of temperature. They are determined as numerical λ-derivatives of the respective quantities computed by thermal full configuration interaction with a perturbation-scaled Hamiltonian, H[over ̂]=H[over ̂]_{0}+λV[over ̂]. Sum-over-states analytical formulas for up to the third-order corrections to these properties are also derived as analytical λ-derivatives. These formulas, which are verified by exact numerical agreement with the benchmark data, are given in terms of the Hirschfelder-Certain degenerate perturbation energies and should be valid for both degenerate and nondegenerate reference states at any temperature down to zero. The results in the canonical ensemble are compared with the same in the grand canonical ensemble.
给出了在广泛温度范围内，正则系综中电子亥姆霍兹自由能、内能和熵的零阶到三阶多体微扰修正的基准数据。这些数据通过对使用微扰缩放哈密顿量(Ĥ = Ĥ_0 + λV̂)的热全组态相互作用计算得到的相应量进行数值(λ)导数确定。还推导了这些性质的三阶以内修正的态求和解析公式作为解析(λ)导数。这些公式通过与基准数据的精确数值一致性得到验证，以赫希费尔德 - 塞尔特定简并微扰能量表示，并且对于任何温度直至零的简并和非简并参考态都应有效。将正则系综中的结果与巨正则系综中的结果进行了比较。
