Local order in liquid potassium-antimony alloys studied by neutron scattering andab initiomolecular dynamics

Abstract

The structure and chemical bonding properties of liquid K-Sb alloys have been investigated using neutron scattering experiments and ab initio molecular-dynamics simulations. For alloys containing between 25 and 50 at. % Sb, the neutron data demonstrate the existence of a well-defined prepeak at Q ∼ 1.15 Å reflecting a pronounced short-range order. The ab initio calculations show that the chemical bonding obeys a generalized Zintl principle, i.e. a formally complete electron transfer from K to Sb. The liquid structure is determined for the "octet" composition K3Sb by charge ordering effects leading to a salt-like atomic arrangement, at the equiatomic composition by the formation of short covalently bonded Sb chains in close analogy to the isoelectronic chalcogen elements in the liquid state.

Structure of the equiatomic liquid alloys K–Sb, K–Bi, and Rb–Bi over a wide temperature range

“…A study on solid alloys of alkali metals and both Sb and Bi 23 explains the strong differences in the bonding behavior of the Sb and the Bi alloys by the more extended nature of the Bi 5p orbitals destabilizing chain structures compared to Sb. A recent ab initio MD study on liquid K-Sb 24 gives an average number of Sb atoms in chain fragments of about 5, which is in good agreement with the chainlength that can be calculated from the coordination numbers of the ''chain constraint''-RMC simulation of our scattering data. They also compared experimental structure factors with structure factors resulting from their MD configurations, and found a good agreement.…”

Local atomic and electronic structures of equiatomic liquid alloy KSb from 923 to 1773K

“…For example, the atom number in the longest chain is 7.0 at 923 K, and 5.5 at 1773 K. Therefore, the covalent Sb chains tend to break into shorter pieces, even isolated atoms when temperature is increasing. Bergman et al [22] had studied the structure of liquid KSb using neutron scattering experiments and AIMD simulations and calculated the mean atom number to be six, which is much larger than ours. The reason is that the upper limit is about 3.5 Å in their integration to get the coordination number.…”

Atomic dynamics in liquid KxSb1−x alloys

“…[4,5,6] for M-Sb alloys). In the transition from the pure alkali metal to the octet composition, the structural changes are considerable due to the big differences in the electronic structure of a metal and an ionic system.…”