The exotically stoichiometric compounds in Al-S system under high pressure

Abstract

Aluminum and sulfur, as abundant elements in earth, only form Al2S3 in nature at ambient pressure. It has been realized that the stoichiometry of compounds may change under high pressure, which is crucial in the discovery of novel materials. In this work, we systematically perform structure search for Al–S system under pressure. Four binary compounds of Al–S with exotic stoichiometries of AlS, Al2S, Al3S4, and AlS2 are found at high pressure and show exciting physical properties. In particular, Al3S4 becomes a superconductor with a predicted superconducting transition temperature Tc of 20.9 K at 100 GPa, while the pressure-induced Al2S becomes an electride, where the valence electrons of aluminum strongly localize in the interstices, acting as anions, at a pressure of 70 GPa. This work provides a viable direction for further experimental study of the properties of Al–S system.