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First-principles study of metal free electron properties
under nonequilibrium conditions

The electronic behavior of various solid metals (Al, Ni, Cu, Au, Ti and W) under ultrashort laser irradiation is investigated by means of density functional theory. Successive stages of extreme nonequilibrium on picosecond timescale impact the excited material properties in terms of optical coupling and transport characteristics. As these are generally modelled based on the free electron classical theory, the free electron number is a key parameter. However, this parameter remains unclearly defined, and dependencies on the electronic temperature are not considered. Here, from first-principles calculations, densities of states are obtained with respect to electronic temperatures varying from 0.01K to 100 000K. Based on the concept of localized or delocalized electronic states, temperature dependent free electron numbers are evaluated for a series of metals covering a large range of electronic configurations. With the increase of the electronic temperature, we observe strong adjustments of the electronic structures of transition metals, that are related to variations of electronic occupation in partly localized d-bands, via change in electronic screening and electron-ion effective potential. The electronic temperature dependence of nonequilibrium density of states have consequences on electronic chemical potentials, free electron numbers, electronic heat capacities and electronic pressures. These electronic thermodynamic properties are computed and discussed, these data can serve as a base to derive energetic and transport properties allowing the description of excitation and relaxation phenomena caused by rapid laser action.

References:
E. Bévillon, J.P. Colombier, V. Recoules, and R. Stoian, “First-principles study of metal free electron properties under nonequilibrium conditions”, submitted to Physical Review B (2013).

Resources:
Find below the electronic Densities Of States (DOS) for each metal for 11 electronic temperatures. The original energy resolution and range used for the publication (including semicore states) can be obtained on request (e-mail [emile.bevillon@univ-st-etienne.fr] or [jean.philippe.colombier@univ-st-etienne.fr]).

[Al_DOS.dat [DAT - 1 Mo]]
[Ni_DOS.dat [DAT - 1 Mo]]
[Cu_DOS.dat [DAT - 1 Mo]]
[Au_DOS.dat [DAT - 1 Mo]]
[Ti_DOS.dat [DAT - 1 Mo]]
[W_DOS.dat [DAT - 1 Mo]]

In the animated pictures below, DOS displacement and shrink discussed in the article are clearly visible: