Emerging Yttrium Phosphides with Tetrahedron Phosphorus and Superconductivity under High Pressures.

Metal phosphides have triggered growing interest for their exotic structures and striking properties. Hence, within advanced structure search and first-principle calculations, several unprecedented Y-P compounds (e. g., Y3 P, Y2 P, Y3 P2 , Y2 P3 , YP2 , and YP3 ) were identified under compression. Interestingly, as phosphorus content increases, P atoms exhibit diverse behaviors corresponding to standalone anion, dumbbell, zigzag chain, planar sheet, crossing chain-like network, buckled layer, three-dimensional framework, and wrinkled layer. Particularly, Fd-3m YP2 can be viewed as assemblage of diamond-like Y structure and rare vertex-sharing tetrahedral P4  units. Impressively, electron-phonon coupling (EPC) calculations elucidate that Pm-3m Y3 P possesses the highest superconducting critical temperature Tc of 10.2 K among binary transition metal phosphides. Remarkably, the EPC of Pm-3m Y3 P mainly arises from the contribution of low-frequency soft phonon modes, whereas mid-frequency phonon modes of Fd-3m YP2 dominate. These results strengthen knowledge of metal phosphides and pave a way for seeking superconductive transition metal phosphides.