Understanding redox and photochemical reactions in aqueous environments requires a precise knowledge of the ionization potential and electron affinity of liquid water. The former has been measured, but not the latter. We predict the electron affinity of liquid water and of its surface from first principles, coupling path-integral molecular dynamics with ab initio potentials, and many-body perturbation theory. Our results for the surface (0.8 eV) agree well with recent pump-probe spectroscopy measurements on amorphous ice. Those for the bulk (0.1-0.3 eV) differ from several estimates adopted in the literature, which we critically revisit. We show that the ionization potential of the bulk and surface are almost identical; instead their electron affinities differ substantially, with the conduction band edge of the surface much deeper in energy than that of the bulk. We also discuss the significant impact of nuclear quantum effects on the fundamental gap and band edges of the liquid.

中文翻译：

---

液态水的电子亲和力。

要了解水性环境中的氧化还原和光化学反应，需要对液态水的电离势和电子亲和力有确切的了解。前者已测量，但后者未测量。我们从第一性原理，耦合路径-整体分子动力学与从头算势以及多体扰动理论等方面预测液态水及其表面的电子亲和力。我们的表面（0.8 eV）结果与最近在无定形冰上的泵浦探针光谱测量结果非常吻合。大部分（0.1-0.3 eV）的估算值与文献中采用的几种估算值不同，我们对此进行了严格的重新评估。我们显示出本体和表面的电离势几乎相同；相反，它们的电子亲和力相差很大，表面的导带边缘的能量比块体的能量深得多。我们还将讨论核量子效应对液体的基本能隙和能带边缘的重大影响。