title: Zero-Point Energy Leakage in Quantum Thermal Bath Molecular Dynamics Simulations.
abstract: The quantum thermal bath (QTB) has been presented as an alternative to path-integral-based methods to introduce nuclear quantum effects in molecular dynamics simulations. The method has proved to be efficient, yielding accurate results for various systems. However, the QTB method is prone to zero-point energy leakage (ZPEL) in highly anharmonic systems. This is a well-known problem in methods based on classical trajectories where part of the energy of the high-frequency modes is transferred to the low-frequency modes leading to a wrong energy distribution. In some cases, the ZPEL can have dramatic consequences on the properties of the system. Thus, we investigate the ZPEL by testing the QTB method on selected systems with increasing complexity in order to study the conditions and the parameters that influence the leakage. We also analyze the consequences of the ZPEL on the structural and vibrational properties of the system. We find that the leakage is particularly dependent on the damping coefficient and that increasing its value can reduce and, in some cases, completely remove the ZPEL. When using sufficiently high values for the damping coefficient, the expected energy distribution among the vibrational modes is ensured. In this case, the QTB method gives very encouraging results. In particular, the structural properties are well-reproduced. The dynamical properties should be regarded with caution although valuable information can still be extracted from the vibrational spectrum, even for large values of the damping term.
authors.affiliation: Laboratoire Structures Propriétés et Modélisation des Solides, CentraleSupélec, CNRS, Université Paris-Saclay , 92295 Châtenay-Malabry, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Brieuc
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06 , CNRS, Institut des Nanosciences de Paris (INSP), 4 Place Jussieu, 75252 Paris, France.
authors.forename: Yael
authors.initials: Y
authors.lastname: Bronstein
authors.affiliation: Laboratoire Structures Propriétés et Modélisation des Solides, CentraleSupélec, CNRS, Université Paris-Saclay , 92295 Châtenay-Malabry, France.|Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA, Université Paris-Saclay , 91128 Palaiseau, France.
authors.forename: Hichem
authors.initials: H
authors.lastname: Dammak
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06 , CNRS, Institut des Nanosciences de Paris (INSP), 4 Place Jussieu, 75252 Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Depondt
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06 , CNRS, Institut des Nanosciences de Paris (INSP), 4 Place Jussieu, 75252 Paris, France.
authors.forename: Fabio
authors.initials: F
authors.lastname: Finocchi
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA, Université Paris-Saclay , 91128 Palaiseau, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Hayoun