An observable for vacancy characterization and diffusion in crystals
Abstract
To locate the position and characterize the dynamics of a vacancy in a crystal, we propose to represent it by the ground state density of a quantum probe quasi-particle for the Hamiltonian associated to the potential energy field generated by the atoms in the sample. In this description, the h^2/2mu coefficient of the kinetic energy term is a tunable parameter controlling the density localization in the regions of relevant minima of the potential energy field. Based on this description, we derive a set of collective variables that we use in rare event simulations to identify some of the vacancy diffusion paths in a 2D crystal. Our simulations reveal, in addition to the simple and expected nearest neighbor hopping path, a collective migration mechanism of the vacancy. This mechanism involves several lattice sites and produces a long range migration of the vacancy. Finally, we also observed a vacancy induced crystal reorientation process.
Cite
@article{arxiv.1204.0192,
title = {An observable for vacancy characterization and diffusion in crystals},
author = {Pierre-Antoine Geslin and Giovanni Ciccotti and Eric Vanden-Eijnden and Simone Meloni},
journal= {arXiv preprint arXiv:1204.0192},
year = {2013}
}