Efficient capturing of nuclear quantum effects in high-pressure systems with nuclear-electronic orbital theory

by Dr Paolo Settembri (PSI)

Wednesday 28 Jan 2026, 15:00 → 16:00 Europe/Zurich

OVGA/200

Nuclear quantum effects are essential to correctly describe certain hydrogen systems at high pressures. Superconducting hydrides and ice are prime examples of such systems, requiring the inclusion of lattice anharmonicity and nuclear quantum effects to correctly predict and describe the crystal structures and phase transition pressures observed experimentally. 
In this seminar, I will introduce the nuclear–electronic orbital (NEO) density functional theory method, which treats nuclei quantum mechanically on the same level as the electrons, and demonstrate its ability to capture nuclear quantum effects in superconducting hydrides and ice. 
I will present our results regarding the reproduction of the hydrogen-bond symmetrization pressure in H3S and D3S, benchmarked against the stochastic self-consistent harmonic approximation (SSCHA) method; the prediction of the correct symmetric Fm-3m structure for LaH10; and the estimation of the Ice-VIII to Ice-X phase transition pressure in agreement with experimental measurements. 
Finally, I will argue how the accuracy, computational efficiency, and broad applicability of the NEO method pave the way for expanded large-scale studies of these systems,  as well as new developments designed to further extend its potential applications.