Absolute energy levels of liquid water from many-body perturbation theory with effective vertex corrections

We demonstrate the importance of addressing the 𝚪 vertex and thus going beyond the GW approximation for achieving the energy levels of liquid water in many- body perturbation theory. In particular, we consider an effective vertex function in both the polarizability and the self-energy, which does not produce any computational overhead compared with the GW approximation. We yield the band gap, the ionization potential, and the electron affinity in good agreement with experiment and with a hybrid functional description. The achieved electronic structure and dielectric screening further lead to a good description of the optical absorption spectrum, as obtained through the solution of the Bethe–Salpeter equation. In particular, the experimental peak position of the exciton is accurately reproduced.

本研究阐述了在多体扰动理论中，处理𝚪顶点的重要性，并超越了GW近似，以实现液态水的能级。具体而言，我们考虑了极化率和自能中的有效顶点函数，该函数与GW近似相比，不产生任何额外的计算开销。我们得到了与实验结果良好一致的能隙、电离势和电子亲和力，并使用混合泛函描述。所实现的电子结构和介电屏蔽进一步导致了光学吸收光谱的良好描述，这是通过贝特-萨普特方程的求解获得的。特别是，激子实验峰值位置得到了精确的再现。