Unusual coordination structure in undercooled eutectic Ga-In alloy melt.

The local structures in the normal and undercooled liquid eutectic Ga-In alloy are investigated by using X-ray absorption spectroscope (XAS), X-ray diffractometer (XRD) and the ab initio molecular dynamics (AIMD) simulations. The results from these three techniques all indicate that the nearest-neighbor coordination number decreases with decreasing temperature in the liquid eutectic Ga-In alloy. Moreover, the nearest-neighbor interatomic distance increases and the local atomic packing density decreases with decreasing temperature. The X-ray absorption near edge structure (XANES) measurement shows that the atomic rearrangement at the undercooled temperature results in the formation of low-coordinated polyhedron clusters with high symmetries. This finding provides a new perspective for understanding the liquid-solid transition in undercooled conditions. [ABSTRACT FROM AUTHOR]