Structure of liquid potassium-antimony alloys: neutron scattering experiments and ab initio molecular dynamics calculations

Neutron scattering measurements have been performed on liquid potassium-ant imony alloys at x(Sb) = 0.15, 0.25, 0.4 and 0.5 in the temperature range 82 0 < T(K) < 1100 depending on the composition. These compositions are chosen according to the specific features of the phase diagram. The total structu re factors are determined and they exhibit a well-defined prepeak at q = 1. 15 Angstrom(-1) for all the alloys except the K-rich one. The pair correlat ion functions are then obtained. The experimental results show a tendency f or segregation at x(Sb) = 0.15 Ab initio density-functional molecular dynam ics (MD) studies have been performed for the liquid alloys with x(Sb) = 0.2 5 and 0.5 and for the crystalline intermetallic compounds K3Sb, K5Sb4 and K Sb. Theory and experiment agree on the existence of a salt-like order at th e octet composition, changing continuously to a polyanionic order with chai n-like Sb-clusters at equiatomic compositions. (C) 1999 Elsevier Science B. V. All rights reserved.