Temperature-induced structural evolution in liquid Ag-Ga alloys

Abstract

Temperature-dependent atomic structural evolutions of liquid ${\mathrm{Ag}}_{60}{\mathrm{Ga}}_{40}$ and ${\mathrm{Ag}}_{70}{\mathrm{Ga}}_{30}$ alloys have been studied by in situ high-energy x-ray-diffraction (HEXRD) experiments combined with ab initio molecular-dynamics simulations. The experimental data show a reversible structural crossover at about $1050\ensuremath{\sim}1100 (\ifmmode\pm\else\textpm\fi{}50)\phantom{\rule{4pt}{0ex}}\mathrm{K}$ in both liquid ${\mathrm{Ag}}_{60}{\mathrm{Ga}}_{40}$ and ${\mathrm{Ag}}_{70}{\mathrm{Ga}}_{30}$ alloys. Obvious changes of the electrical resistivity, absolute thermoelectric power, and atomic diffusivity around the similar temperature range for both Ag-Ga liquids strongly support the HEXRD results. The origin of the liquid-to-liquid crossover in both Ag-Ga liquids was suggested to link with the rearrangements of Ag and Ga atoms, i.e., Ag and Ga atoms prefer to associate with themselves in the higher temperature range above 1100 K, consistent with the accelerated increase of the strong covalently bonded Ga--Ga dimers in both Ag-Ga liquids. In addition, more studies from the energy aspect are still desirable to understand the rearrangements of Ag and Ga atoms in the higher temperature range in both Ag-Ga liquids.