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

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 disper- sive 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.