Surface structure in simple liquid metals. An orbital free first principles study

摘要

Molecular dynamics simulations of the liquid-vapour interfaces in simplesp-bonded liquid metals have been performed using first principles methods.Results are presented for liquid Li, Na, K, Rb, Cs, Mg, Ba, Al, Tl, and Si atthermodynamic conditions near their respective triple points, for samples of2000 particles in a slab geometry. The longitudinal ionic density profilesexhibit a pronounced stratification extending several atomic diameters into thebulk, which is a feature already experimentally observed in liquid K, Ga, In,Sn and Hg. The wavelength of the ionic oscillations shows a good scaling withthe radii of the associated Wigner-Seitz spheres. The structural rearrangementsat the interface are analyzed in terms of the transverse pair correlationfunction, the coordination number and the bond-angle distribution betweennearest neighbors. The valence electronic density profile also shows (weaker)oscillations whose phase, with respect to those of the ionic profile, changesfrom opposite phase in the alkalis to almost in-phase for Si.