About the computation of finite temperature ensemble averages of hybrid quantum-classical systems with molecular dynamics
Abstract
Molecular or condensed matter systems are often well approximated by hybrid quantum-classical models: the electrons retain their quantum character, whereas the ions are considered to be classical particles. We discuss various alternative approaches for the computation of equilibrium (canonical) ensemble averages for observables of these hybrid quantum-classical systems through the use of molecular dynamics (MD)-i.e. by performing dynamics in the presence of a thermostat and computing time-averages over the trajectories. Often, in classical or ab initio MD, the temperature of the electrons is ignored and they are assumed to remain at the instantaneous ground state given by each ionic configuration during the evolution. Here, however, we discuss the general case that considers both classical and quantum subsystems at finite temperature canonical equilibrium. Inspired by a recent formal derivation for the canonical ensemble for quantum classical hybrids, we discuss previous approaches found in the literature, and provide some new formulas.
- Publication:
-
New Journal of Physics
- Pub Date:
- June 2021
- DOI:
- 10.1088/1367-2630/abf9b3
- arXiv:
- arXiv:2105.02538
- Bibcode:
- 2021NJPh...23f3011A
- Keywords:
-
- molecular dynamics;
- Ehrenfest dynamics;
- hybrid quantum classical dynamics;
- hybrid canonical ensemble;
- finite temperature;
- ergodic trajectories;
- Physics - Chemical Physics;
- Condensed Matter - Statistical Mechanics;
- Quantum Physics
- E-Print:
- This is the version of the article before peer review or editing, as submitted by an author to New Journal of Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1367-2630/abf9b3