Structural and electronic properties of liquid alkali–tin alloys

Abstract

There is a debate about the preservation of tetrahedral polyanions formed in crystalline equiatomic (Na/K/Rb/Cs)–(Sn/Pb) compounds on melting. Diffraction experiments demonstrate the existence of a narrow first diffraction peak in the static structure factor indicative of local ordering. On the other hand reverse Monte-Carlo calculations and classical as well as quantum-mechanical simulations have failed to confirm the existence of polyanionic complexes in a liquid phase. We present ab initio local density functional studies of the structural and electronic properties of crystalline and liquid (Li/Na/K)–Sn alloys. While our calculations demonstrate the existence of tetrahedral complexes in KSn, for NaSn they agree with previous conclusions that the Sn 4 4−-tetrahedra are distorted or even destroyed in the liquid. For the liquid LiSn alloy we demonstrate that, due to the small size of the Li-ion, interactions between the Sn-ions destabilize the polyanionic order.