Local Correlations In Liquid and Supercooled Gallium Probed By X-ray-absorption Spectroscopy

An investigation on the local structure of liquid and supercooled pure gallium at several temperatures is presented. Accurate EXAFS (Extended X-ray Absorption Fine Structure) spectra have been analysed by means of ab initio calculations of the multiple-scattering signals associated with two-atom and three-atom configurations. The extracted g2(r) first-neighbour distribution of the liquid phase was found to be in excellent agreement with diffraction measurements. Clear evidence of nearly covalent bonds has been found in highly supercooled gallium where the asymmetric first-neighbour distribution is split into two resolved peaks. Analysis of the three-atom g3(r1, r2, theta) distribution has shown evidence for nearly-equilateral and nearly-orthogonal configurations