Local structure of liquid gallium studied by X-ray absorption fine structure

Abstract

X-ray absorption fine structure (XAFS) has been used to study the local structures of Ga in the temperature region between 78 and 373 K. The three model atomic pair distribution functions, i.e. Gaussian function, convolution of Gaussian and exponent function, and cumulant expansion, are used to analyze EXAFS data of the liquid Ga. Assuming an asymmetric atom pair distribution function made from the convolution of Gaussian, P G, and exponent function, P E, we have obtained the structure parameters for liquid Ga (305 K): average bond length, R=2.92 A ̊ , coordination number, N=9.8, thermal disorder parameter, σ T =0.07 A ̊ and static disorder parameter, σ S =0.12 A ̊ . Although the short Ga–Ga covalent bond (2.44 A ̊ ) is not observed for liquid Ga, the Ga atoms in the first coordination shell are distributed in a wide R region centered at 2.92 A ̊ . Based on these results, we propose that the coordination geometry changes from the distorted body centered cubic ( N=7) to the distorted body centered tetragonal ( N=10) associated with a solid–liquid phase transition.