Ion-electron correlations in liquid metals from orbital-free ab initio molecular dynamics

Extensive ab initio molecular-dynamics (AIMD) simulations have been performed for liquid Na, Mg, and Al, three metals having the same core of 10 electrons but with a different number of valence electrons. The calculations have been carried out with the orbital-free version of the Car-Parrinello technique. Results were obtained for the functions that describe the ion-ion and ion-electron correlations. Comparison of these with results of those from standard Kohn-Sham AIMD confirms the ability of the orbital-free scheme to provide correct properties from first principles at a reasonable computational cost. The results presented here demonstrate that the overall ion-electron correlations predicted by simulation differ substantially from the experimental data so far reported for this property. This observation is closely related to the fact that, according to the theory, the difference between x-ray and neutron-diffraction structure factors should be much smaller than that encountered in the experiments.