Modeling Liquid Photoemission Spectra: Path-Integral Molecular Dynamics Combined with Tuned Range-Separated Hybrid...

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Spectroscopy

Background:

• Modeling valence photoemission spectra of liquids is complex.
• Accurate simulation requires accounting for nuclear quantum effects and electronic relaxation.
• Liquid water serves as a well-characterized benchmark system.

Purpose of the Study:

• To present a computational protocol for modeling valence photoemission spectra of liquids.
• To quantitatively describe the spectrum of liquid water, including peak positions, shapes, and widths.
• To investigate the convergence of electronic properties from finite-sized droplets to bulk liquids.

Main Methods:

• Utilized finite-sized liquid water droplets in molecular dynamics simulations.
• Incorporated nuclear quantum effects using ab initio path-integral molecular dynamics with colored noise thermostat (PI+GLE).
• Calculated ionization energies using optimally tuned range-separated hybrid functionals (OT-RSH) for Koopmans-type energies including relaxation.

Main Results:

• The protocol quantitatively reproduces the valence photoemission spectrum of liquid water.
• PI+GLE simulations successfully modeled subtle isotope effects observed experimentally.
• Electronic properties of finite droplets rapidly converge to bulk liquid properties.

Conclusions:

• The developed computational protocol is a viable method for modeling liquid photoemission spectra.
• Accurate tuning of range-separation parameters in OT-RSH is crucial.
• The approach shows promise, especially with efficient GPU implementations of density functional methods.