Prediction of superconductivity in pressure-induced new silicon boride phases

Abstract

The crystal structures and properties of boron-silicon (B-Si) compounds under pressure have been systematically explored using particle swarm optimization structure prediction method in combination with first-principles calculations. Three new stoichiometries, B 2 Si, BSi, and BSi 2 , are predicted to be stable gradually under pressure, where increasing pressure favors the formation of silicon rich B-Si compounds. In the boron-rich compounds, the network of boron atoms changes from B 12 icosahedron in the ambient phases to the similar buckled graphenelike layers in the high-pressure phases, which crystalize in the same P3m1 symmetry but with different numbers of boron layers between adjacent silicon layers. Phonon calculations show that these structures might be retained to ambient conditions as metastable phases. Further electron-phonon coupling calculations indicate that the high-pressure phases of boron-rich compounds might superconduct at 1 atm, with the highest T c value of 21 K from the Allen-Dynes equation in P3m1 B 2 Si, which is much higher than the one observed in boron doped diamond-type silicon. Moreover, further fully anisotropic Migdal-Eliashberg calculations indicate that B 2 Si is a two-gap anisotropic superconductor and the estimated T c might reach up to 30 K at 1 atm. On the silicon-rich side, BSi 2 is predicted to be stable in the CuAl 2 -type structure. Our current results significantly enrich the phase diagram of the B-Si system and will stimulate further experimental study.

Double-dome superconductivity in germanium phosphides

“…This behavior can be explained by the results that the optical branches and the spectral function a 2 F(o) of I4/m have a rather uniform shift to higher energy, which can be attributed to more P atom vibrations. For another, o log is the other main ingredient to estimate l and T c 51,52 according to eqn (1). As shown in our calculated o log in Fig.…”

Pressure-Driven Structural Phase Transitions and Superconductivity of Ternary Hydride MgVH6

“…per simulation cell at pressures of 50, 100, 150, and 200 GPa by using the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) , and the Vienna ab initio simulation package (VASP) . CALYPSO has been successfully applied to various systems. − The predicted low-energy structures are relaxed fully within pressure up to 200 GPa by means of VASP. In these calculations, the Perdew-Burke-Ernzerh form (PBE) of the generalized gradient approximation (GGA) is employed .…”

Emergent superconductivity in K2ReH9 under pressure

“…On the other hand, ternary hydrides have attracted much attention owing to their novel structures and intriguing superconductivity induced by synergistic charge transfer. 5 Although, a wealth of ternary hydrides with the sizable T c values (e.g., T c = 473 K at 250 GPa for Li 2 MgH 16 , 26 T c = 195 K at 200 GPa for H 6 SSe, 27 and T c = 258 K at 200 GPa for CaYH 12 28 ) are theoretically reported, these systems may be elusive for synthesis because of their complicated stoichiometries, ultrahigh pressure, the selection of precursors, and other factors of stability. 29 Alternatively, pressure-induced structural phase transition of the known ternary hydrides may be an effective route for preparing superconductors with explicit stoichiometries and structures at lower pressure.…”