Charge transfer within clusters in liquid ionic alloys

Abstract

Based on the Kohn-Sham equations of the density functional formalism and using the pseudopotential approximation, self-consistent calculations of the electron density distribution and structural stability in the Pb₄Na₄ and Pb₄Cs₄ clusters have been carried out. For the two clusters, the geometrical structures are similar: the Pb atoms are arranged in a regular tetrahedron inside, while the alkali metal atoms (Na or Cs) form a larger tetrahedron outside taking positions opposite to the faces of the Pb₄ unit. The charge transfer from the outer alkali metal atoms to the inner Pb₄ tetrahedron increases with decreasing electronegativity of the alkali metal atom. The net excess of charge in the Pb₄ unit is of the order of one electronic charge. The authors used their results to discuss the liquid alloys Pb_0.5Na_0.5 and Pb_0.5Cs_0.5, where much higher charge transfer is normally assumed.