Experimental and computational study of the liquid-solid transition in tin.

Abstract

An experimental technique was developed to perform isentropic compression of heated liquid tin samples at the Z Accelerator, and multiple such experiments were performed to investigate solidification under rapid compression. Preliminary analyses, using two different methods, of data from experiments with high uncertainty in sample thickness suggest that solidification can begin to occur during isentropic compression on time scales of less than 100 ns. Repeatability of this result has not been confirmed due to technical issues on the subsequent experiments performed. First-principles molecular-dynamics calculations based on density-functional theory showed good agreement with experimentally-determined structure factors for liquid tin, and were used to investigate the equation of state and develop a novel interatomic pseudo-potential for liquid tin and its high-pressure solid phase. Empirical-potential molecular-dynamics calculations, using the new potential, gave results for the solid-liquid interface velocity, which was found to vary linearly with difference in free energy between the solid and liquid phases, as well as the liquidus, the maximum over-pressurization, and the solid-liquid interfacial energy. These data will prove useful in future modeling of solidification kinetics for liquid tin. Stephen Foiles would like to acknowledge many useful discussions with J. J. Hoyt (Org. 1814) concerning the simulation of solid-liquid interfaces. Aidan Thompson (Org. 1435) incorporated the new interatomic potential into the parallel molecular dynamics code, GRASP. Finally, Marcus Martin (Org. 1435) provided important advice on the use of the DAKOTA software package for the determination of interatomic potentials.