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arXiv · 1204.0192

An observable for vacancy characterization and diffusion in crystals

Pierre-Antoine Geslin·Giovanni Ciccotti·Eric Vanden-Eijnden·Simone Meloni
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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.

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Pierre-Antoine Geslin, Giovanni Ciccotti, Eric Vanden-Eijnden, Simone Meloni. 2012-04-01. An observable for vacancy characterization and diffusion in crystals. https://doi.org/10.1063/1.4796322

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