Study On High Temperature And High Pressure Of Bi-S Binary System

Under high pressure,many materials will exhibit rich phase transition behavior.It is particularly important to deeply understand the mechanism of electronic topological phase transition and structural phase transition under high pressure.The metal elements in the transition metal sulfur compounds have unfilled d orbitals,especially 5d transition metal sulfides,which have strong spin orbit coupling?SOC?interactions and are rich in physical properties.These singular properties are very sensitive to adjustable parameters such as pressure,temperature,and doping.At the same time,the discovery of compounds with other structural forms and other stoichiometric ratios under high pressure is also of great concern.Based on the above knowledge,we conducted a study on the stability and structural phase evolution of Bi-S binary compounds under extreme conditions of high temperature and high pressure.First,X-ray diffraction at room temperature and high-pressure synchrotron radiation shows that the Bi₂S₃ crystal structure is stable,and the pressure-induced disordered amorphization of the structure occurs at48GPa.The nonlinear behavior of the lattice parameter ratio c/a with pressure changes is likely to be around 4GPa.An electronic topological phase change has occurred.Subsequent high-voltage electrical transport properties tests confirmed the results of synchrotron radiation X-rays,and the density of electron states near the Fermi level was rearranged under pressure.This reconstruction of the Fermi surface is often accomxbany by strong anisotropy The lattice of the lattice is reduced,so the lattice parameter ratio c/a and the pressure-dependent change are non-linear.Secondly,we prepared a new stoichiometric cubic BiS crystal of Bi-S system by laser heating high temperature and high pressure experimental method.Laser heating high temperature and high pressure synchrotron radiation X-ray diffraction experiments show that Bi₂S₃ is thermodynamically unstable and decomposes into a new type of stoichiometric cubic BiS and element S,which is consistent with previous theoretical predictions that BiS is more stable when the pressure is higher than 19GPa Match.The new stoichiometric BiS is a cubic crystal system with a space group of pm-3m and a lattice constant of a=2.894?.Cubic BiS compounds can be preserved from high temperature and high pressure quenching to room temperature conditions.The theoretical predictions show that BiS has interesting metals Behavior and potential superconducting properties.