A model to incorporate electron phonon coupling into classical molecular dynamics*

We have developed a new model to incorporate equilibration of ions and electrons at the corresponding timescales into classical molecular dynamics (MD) simulations. The model is based on Langevin dynamics where the stochastic description does not generate any linear momentum nor torque in the system. This is achieved by introducing spatial correlations into friction and random forces which have a range described by atomic electron density.
All the model parameters can be described fully by using results from first principles realtime time-dependent density functional theory calculations. We use this model to study the phonon lifetimes due to electron-phonon coupling in classical MD simulations in large and complex systems. Particularly, our model is able to capture the wavevector and polarisation dependence of phonon lifetimes in qualitatively good agreement with more exact methods.
Finally, we apply the model to study the laser heating of a material similar to pump-probe laser experiments. In conclusion, this model should be used to study the dynamics of any metallic system where the electronic and lattice temperatures diverge due to fast phenomena, like, radiation damage, laser-material interaction, and compressions shocks.