Hydrogen and muonium in diamond: A path-integral molecular dynamics simulation

TL;DR

This study uses path-integral molecular dynamics to analyze the behavior of hydrogen, deuterium, and muonium impurities in diamond, revealing their stable positions, vibrational properties, and electronic effects at finite temperatures.

Contribution

It introduces a detailed simulation approach combining path-integral molecular dynamics with a tight-binding potential to study hydrogenic impurities in diamond, highlighting anharmonic vibrations and electron-phonon interactions.

Findings

Hydrogenic impurities prefer the C-C bond center site.

Impurity vibrations exhibit significant anharmonicity at finite temperatures.

Zero-point motion shifts defect levels in the electronic gap, with muonium lowering the level by 70 meV.

Abstract

Isolated hydrogen, deuterium, and muonium in diamond have been studied by path-integral molecular dynamics simulations in the canonical ensemble. Finite-temperature properties of these point defects were analyzed in the range from 100 to 800 K. Interatomic interactions were modeled by a tight-binding potential fitted to density-functional calculations. The most stable position for these hydrogenic impurities is found at the C-C bond center. Vibrational frequencies have been obtained from a linear-response approach, based on correlations of atom displacements at finite temperatures. The results show a large anharmonic effect in impurity vibrations at the bond center site, which hardens the vibrational modes with respect to a harmonic approximation. Zero-point motion causes an appreciable shift of the defect level in the electronic gap, as a consequence of electron-phonon interaction. This defect level goes down by 70 meV when replacing hydrogen by muonium.