Exploration of Stable Strontium Phosphide-Based Electrides: Theoretical Structure Prediction and Experimental Validation.

Inspired by the successful synthesis of alkaline-earth-metals-based electrides [Ca24 Al28 O64 ]4+ (e- )4 (C12A7:e- ) and [Ca2 N]+ :e- and high-throughput database screening results, we explore the potential for new electrides to emerge in the Sr-P system through a research approach combining ab initio evolutionary structure searches and experimental validation. Through employing an extensive evolutionary structure search and first-principles calculations, we first predict the new structures of a series of strontium phosphides: Sr5 P3 , Sr8 P5 , Sr3 P2 and Sr4 P3 . Of these structures, we identify Sr5 P3 and Sr8 P5 as being potential electrides with quasi-one-dimensional (1D) and zero-dimensional (0D) character, respectively. Following these theoretical results, we present the successful synthesis of the new compound Sr5 P3 and the experimental confirmation of its structure. Although density functional calculations with the generalized gradient approximation predict Sr5 P3 to be a metal, electrical conductivity measurement reveal semiconducting properties characterized by a distinct band gap, which indicates that the newly synthesized Sr5 P3 is an ideal one-dimensional electride with the half-filled band by unpaired electrons. In addition to presenting the novel electride Sr5 P3 , we discuss the implications of its semiconducting nature for 1D electrides in general and propose a mechanism for the formation of electrides with an orbital level diagram based on first-principles calculations.