Physics

Electron

Organic chemistry

Crystallography

Amorphous ice

Ionization energy

Physical chemistry

Band gap

Atomic physics

Chemical physics

Aqueous solution

Chemistry

Materials science

Ionization

Condensed matter physics

Liquid water

Molecule

Molecular physics

Amorphous solid

Quantum mechanics

Electron affinity (data page)

Thermodynamics

Nature Communications

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.

Electron affinity of liquid water