Electron-phonon coupling using DFT based molecular dynamics

Contexte :

The advent of femtosecond lasers has shed a new light on non-equilibrium physics. The ultrafast energy absorption by electrons and the finite rate of their energy transfer to the lattice create non-equilibrium states of matter, triggering a new class of non-thermal processes from the ambient solid up to extreme conditions of temperature and pressure. The dynamical interplay between electrons and the atomic structure is the key issue that drives the ultrafast phase transitions dynamics. The heat transfer rate between electron and ions is accounted for by electron-phonon scattering. This electron-phonon coupling is a crucial input, there is still a controversy on the description of this coupling constant for two-temperature systems. The goal of this post-doc is to advance the theoretical formulation for electron-phonon coupling and implement the new formulation in a electronic structure code based on Density Functional Theory.

Objectif :

The time evolution of the electronic and ionic temperature can be described by rate equations in what is known as Two Temperature Models (TTM). The heat transfer rate is accounted for by electron-phonon scattering and electron-phonon coupling is a crucial input for the TTM. At this time, there is still a controversy on the description of this coupling constant for two-temperature systems as they go from solid states to liquid then to plasma. During this transformation, matter reach extreme conditions of temperature (up to ~30000K) and pressure (up to ~100GPa). This seriously challenges theoretical calculation of time evolution of the electronic structure of two-temperature solids. The solid states physics approach considers that the electron kinetic is transferred to the degrees of freedom of bound ions, described as phonons. On the other side the plasmas physics approaches consider the scattering of electrons with plasmons. Recently, new formulations were proposed using Time Dependent DFT.
During this post-doc, the candidate will have to find the formulation for the electron-phonon coupling suitable for warm dense matter starting from the most recent publications. This formulation will be then implemented in a ab initio code. At last, the candidate will run DFT based molecular dynamics simulations on massively parallel computers to obtain the electron phonon coupling for two-temperatures metals at extreme conditions. All implementation and calculation will be done with ABINIT code. All this work will be done in close interaction with people running classical molecular dynamics and experimental teams.

CENTRE

DAM – Île-de-France
Bruyères-le-Châtel – 91297 Arpajon
01-69-26-40-00

CONTACTS

RECOULES Vanina
vanina.recoules@cea.fr
TORRENT Marc
marc.torrent@cea.fr