Vibrational properties and diffusion of hydrogen on graphene

TL;DR

This study uses path-integral molecular dynamics to analyze vibrational properties and diffusion of hydrogen on graphene, revealing significant anharmonicity and quantum effects that enhance hydrogen mobility at room temperature.

Contribution

It provides the first detailed analysis of vibrational anharmonicity and quantum-enhanced diffusion of hydrogen on graphene using advanced simulation techniques.

Findings

Vibrational modes show strong anharmonicity.

Quantum effects increase hydrogen diffusivity by a factor of 20 at room temperature.

Finite-temperature properties of hydrogen on graphene are characterized from 200 to 1500 K.

Abstract

Hydrogen and deuterium chemisorption on a single layer of graphene has been studied by path-integral molecular dynamics simulations. Finite-temperature properties of these point defects were analyzed in the range from 200 to 1500 K, by using a tight-binding potential fitted to density-functional calculations. On one side, vibrational properties of the adatoms are studied at their equilibrium positions, linked to C atoms. The vibrations display an appreciable anharmonicity, as derived from comparison between kinetic and potential energy, as well as between vibrational energy for hydrogen and deuterium. On the other side, adatom motion has been studied by quantum transition-state theory. At room temperature, quantum effects are found to enhance the hydrogen diffusivity on the graphene sheet by a factor of 20.