基态能量的Bethe-Salpeter公式的利弊
Pros and Cons of the Bethe-Salpeter Formalism for Ground-State Energies
摘要：
结合多体格林函数$GW$近似和Bethe-Salpeter方程（BSE）形式，已被证明是含时密度泛函理论（TD-DFT）计算分子系统垂直跃迁能和振子强度的一种有前途的替代方法。由于绝热联系涨落耗散定理（ACFDT），BSE形式也可以用来计算基态相关能。本文研究了几种双原子分子在平衡键长附近的基态势能面的拓扑结构。由于与最先进的计算方法（CC 3）的比较，我们表明ACFDT@BSE是令人惊讶的准确，甚至可以与低阶耦合簇方法（CC 2和CCSD）的总能量和平衡键距方面的考虑系统。然而，我们有时会观察到非物理的不规则性的基态PES与困难的几个$GW$准粒子能量的识别。
英文摘要：
The combination of the many-body Green's function $GW$ approximation and the Bethe-Salpeter equation (BSE) formalism has shown to be a promising alternative to time-dependent density-functional theory (TD-DFT) for computing vertical transition energies and oscillator strengths in molecular systems. The BSE formalism can also be employed to compute ground-state correlation energies thanks to the adiabatic-connection fluctuation-dissipation theorem (ACFDT). Here, we study the topology of the ground-state potential energy surfaces (PES) of several diatomic molecules near their equilibrium bond length. Thanks to comparisons with state-of-art computational approaches (CC3), we show that ACFDT@BSE is surprisingly accurate, and can even compete with lower-order coupled cluster methods (CC2 and CCSD) in terms of total energies and equilibrium bond distances for the considered systems. However, we sometimes observe unphysical irregularities on the ground-state PES in relation with difficulties in the identification of a few $GW$ quasiparticle energies.
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