High pressure superconducting phase of BI3: an ab initio study

Abstract

Using the ab initio evolutionary algorithm for crystal structure prediction, we successfully obtained the high pressure crystal structure of BI₃ with P2₁/c space group, which was characterized as the B₂I₆ dimer analogous to the diborane molecule. This structure has been supported by excellent agreement between the theoretical and experimental equations of state, X-ray diffraction data, and the positive pressure dependence of T_c. Moreover, the P2₁/c structure is both dynamically and mechanically stable through phonon and elastic constants calculations. Further analysis reveals a superconducting mechanism in which the vibrations of iodine atoms dominate the superconductivity of BI₃. In addition, the positive pressure dependence T_c is mainly attributed to the increase of the EPC parameter λ, the logarithmic average phonon frequency ω_log, and the electronic density of states at the Fermi level N(ε_f).