Phonon-phonon interactions in transition metals

TL;DR

This paper calculates phonon self energy due to anharmonicity in all transition metals using perturbation theory, revealing insights into phonon lifetimes and decay processes across different crystal structures.

Contribution

It introduces a symmetry-based method to compute phonon self energy in transition metals, including detailed analysis of decay channels and approximation validity.

Findings

Phonon lifetime is approximately 10^10 seconds.

Peierls approximation is valid for bcc and fcc metals.

Raman active mode in hcp metals decays into acoustic phonons.

Abstract

In this paper the phonon self energy produced by anharmonicity is calculated using second order many body perturbation theory for all bcc, fcc and hcp transition metals. The symmetry properties of the phonon interactions are used to obtain an expression for the self energy as a sum over irreducible triplets, very similar to integration in the irreducible part of the Brillouin zone for one particle properties. The results obtained for transition metals shows that the lifetime is on the order of 10^10 s. Moreover the Peierls approximation for the imaginary part of the self energy is shown to be reasonable for bcc and fcc metals. For hcp metals we show that the Raman active mode decays into a pair of acoustic phonons, their wave vector being located on a surface defined by conservation laws.