Abstract
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.
Highlights
The absence of long-range atomic order in the liquid state makes it challenging to characterize liquid structure
A first-principle study suggests the local structure of liquid gallium is similar to Ga-II or Ga-III23
To shed light on this contradiction, the local structure of liquid gallium is studied under high pressure at ambient temperature using pair distribution function (PDF) analysis in combination with reverse Monte Carlo (RMC) simulation, constraining the densities to those quantified through measurement by X-ray microtomography
Summary
Renfeng Li1,2, Luhong Wang[1], Liangliang Li1,2,3, Tony Yu4, Haiyan Zhao[3,5], Karena W. 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. 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). Application of RMC analysis requires that the sample density should be known. This is challenging for liquids under variable pressure conditions. To shed light on this contradiction, the local structure of liquid gallium is studied under high pressure at ambient temperature using PDF analysis in combination with RMC simulation, constraining the densities to those quantified through measurement by X-ray microtomography
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