Electronic structure, lattice dynamics, and electron-phonon coupling factor of metals under nonequilibrium heating

The paper presents ab initio calculations taken to study the electronic structure, phonon spectrum, and electron-phonon coupling factor G(T-e) of several metals (Ag, Au, Pd, Pt, Rh, Ir, W, and Ta) at different electron temperatures T-e (similar to 10(4) K) and "cold" crystal lattice. We studied the effect of changes in the electronic structure under electron heating on lattice dynamics and the electron-phonon coupling factor. The outcomes of our study suggest that the evolution of lattice dynamics is quite well correlated with changes in the electronic population of the outer d bands with the growing T-e. The decrease in the number of d electrons results in crystal hardening because the Coulomb potential screening of nuclei reduces, while their increase leads to the growth of the electronic screening and lattice softening. Our calculations show that in the initial phase of heating (T-e <20 kK), the increase of the electron temperature in fcc metals may result in both lattice hardening (Pd, Pt) and softening (Rh, Ir), or quite weak changes in lattice dynamics (Ag, Au). However, lattice softening never makes fcc metals lose their dynamic stability. At higher temperatures (T-e > 20 kK), the tendency to lattice hardening always prevails in them. As for the bcc metals, they are found to lose their dynamic stability as the electron temperature increases above 20 kK. It is also shown in this paper that differences in the electronic structures of metals strongly influence the behavior of the electron-phonon coupling factor as dependent on the electron temperature.