Structure Change of Liquid Bismuth just before the Solidification

Abstract

The structure change of bismuth during the liquid-supercool-solid (LSS) transition process was studied by using the energy scanning X-ray method. Through the LSS process, the position of the first peak in the radial distribution function (RDF) moves inside and the coordination number becomes smaller. Subpeaks on the right hand side of the first peak become more pronounced and they are growing up to the figure just before the solidification, which characterized RDF pattern like solid's. These results were compared with the quasicrystalline model assuming the mixed structure of a hexagonal structure and a rhombohedral one. Consequently, it is suggested that there exists a pre-crystalline state with the rhombohedral structure not the same but similar to the solid one just before the solidification. By distorting slightly the pre-crystalline structure, we could simulate the solidification process.