The hole mass in Car–Parrinello molecular dynamics: insights into the dynamics of excitation

Abstract

In the Car–Parrinello molecular dynamics (CPMD) formalism, orbitals can be assigned different effective masses according to whether the orbital is occupied by a hole or an electron, and such masses affect the response of the orbitals to their environment. Inspired by this, we introduce and implement a novel modification of CPMD, HoleMass CPMD, in which a hole, which is a partially empty orbital, is assigned a fictitious mass that is different from fully occupied orbitals. Despite the simplicity of the approach, we find that it solves a key problem in first principles molecule dynamics simulation: for a set of carefully assigned mass values, the method is able to successfully simulate photoinduced chemical reactions, exemplified here by the ring-opening reaction in oxirane within a few femtoseconds, and cyclobutene, within a few picoseconds. Our method can reproduce the CO ring-opening of oxirane, and the correct isomerization sequence for cyclobutene: when the ring opens, the first isomer that forms is the cis isomer, followed by the trans isomer. Our method has been implemented in the Car–Parrinello package of QuantumEspresso and is available as an open-source contribution. The HoleMass CPMD method provides a new quantum chemistry tool for the simulation of excitation dynamics in molecules, and can also be applied for modelling charge localization effects in materials systems.

Graphical abstract: The hole mass in Car–Parrinello molecular dynamics: insights into the dynamics of excitation

Supplementary files

Article information

Article type
Edge Article
Submitted
09 Jan 2025
Accepted
01 May 2025
First published
01 May 2025
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2025, Advance Article

The hole mass in Car–Parrinello molecular dynamics: insights into the dynamics of excitation

S. A. Tawfik and T. R. Walsh, Chem. Sci., 2025, Advance Article , DOI: 10.1039/D5SC00175G

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