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High-pressure and high-temperature x-ray absorption study of liquid and solid gallium

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High-pressure and high-temperature x-ray absorption study of liquid and solid gallium

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Good quality extended x-ray absorption fine structure (EXAFS) spectra near the Ga K edge have been collected in wide pressure and temperature ranges (namely 0–16 GPa, 298–498 K) using the dispersive setup installed at the LURE synchrotron radiation facility and diamond anvil cell as pressure device. Energy dispersive x-ray diffraction data have been also measured in similar thermodynamical conditions. EXAFS spectra are shown to be sensitive to phase transitions occurring at high pressures and temperatures. Occurrence of stable and metastable phases and location of the coexistence lines are discussed in light of the results obtained using both experimental techniques. The phase diagram of pure gallium has been extended considering present experimental results. EXAFS data-analysis is performed using advanced ab initio methods (GNXAS). Accurate information about local structure in solid and liquid gallium at extreme conditions is obtained. The short-range two-body distribution functions are reconstructed by EXAFS for liquid and solid gallium as a function of pressure and temperature.
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... The red dots ( ) represent the thermodynamic conditions in the solid phase, while the blue dots ( ) represent the data points in the liquid phase. The black curve (-) is the melting line of elemental Ga [52], while the blue dashed line (---) represents a linear fit of the melting line of the eutectic GaIn established in the present study. The data points represented by other colors and shapes are from the isothermal XRD experiments of Q. Yu et al [23], in order to compare different results. ...
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... The anomalously low melting temperature and negative melting curve of Ga means simply compressing the element in a pressure cell at ambient-T will cause it to melt, a trait which has been exploited in some low-p diffraction studies to ∼ 2 GPa made in an unheated DAC [307][308][309]. However, there is little deviation in the local structure of liquid Ga in this p-range by comparison with ambient-p measurements [310]. ...
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