Local structure of liquid gallium under pressure

In situ high energy X-ray pair distribution function (PDF) measurements, microtomography and reverse Monte Carlo simulations were used to characterize the local structure of liquid gallium up to 1.9 GPa. This pressure range includes the well-known solid-solid phase transition from Ga-I to Ga-II at low temperature. In term of previous research, the local structure of liquid gallium within this domain was suggested a mixture of two local structures, Ga I and Ga II, based on fitting experimental PDF to known crystal structure, with a controversy. However, our result shows a distinctly different result that the local structure of liquid gallium resembles the atomic arrangement of both gallium phase II and III (the high pressure crystalline phase). A melting mechanism is proposed for Ga, in which the atomic structure of phase Ι breaks up at the onset of melting, providing sufficient free volume for atoms to rearrange, to form the melt.