Structural Studies of Supercritical Fluid Selenium Using X-ray Diffraction and XAFS Techniques.

Abstract

Recent experimental results on the structural properties of expanded fluid Se using X-ray diffraction and XAFS techniques are described. The energy-dispersive X-ray diffraction measurements have been carried out up to the supercritical region including the semiconductor-metal (SC-M) transition region. We have revealed that the twofold coordinated structure is largely preserved even in the metallic region and the bond shortening occurs on the SC-M transition, which has been confirmed by the XAFS measurement. On the basis of these findings we propose the idea that the existence of the small chain molecule with the planar zig-zag conformation may cause the transition to the metallic state.