Pressure-Induced Structural Phase Transition and Superconductivity in NaSn₅

Abstract

The structural and electronic properties of tin-rich compound NaSn5 were investigated under pressure up to 10 GPa based on the evolutionary algorithm (EA) technique coupled with first-principles total energy calculations. Upon compression, the known metallic tetragonal P-421m phase transforms into a metallic hexagonal P6/mmm phase at 1.85 GPa accompanied by an unusual change of existing form of Sn atoms. The P6/mmm phase can be interpreted as a quasi-layered sandwich structure with two Sn layers and one sodium layer. The presence of softening phonon modes and the existence of Fermi pockets together with the obvious Fermi surface nesting indicate a strong electron-phonon coupling (EPC) and thus potential superconductivity in P6/mmm phase. The strong EPC in P6/mmm phase is mainly attributed to the phonons from Sn1 atoms together with electrons from the Sn1-py and Sn1-pz states. The calculated superconducting critical temperature Tc of the P6/mmm phase is 5.91 K at 1.85 GPa. This study provides a new clue for designing intercalated compounds with superconductivity.

One Structure, Two Elements—LuGe2 Superconductor vs Ordinary Metallic Conductor LuSn2. A Case Study on How Site-Selective Germanium for Tin Atom Substitution Leads to Modulating of the Charge Distribution

“…The overall effect is the changes in the overall charge distribution square nets are modulating the physical properties in these Ge-substituted compounds. According to the literature, − many synthesized under high-pressure (HP) compounds exhibit superconductivity, while other stable at ambient pressure phases are not superconductors. It could be reasoned that the emergence of superconductivity in the HP-phases could be viewed as a consequence of their instability, and likely due to the structural distortion or instabilities, which generally induce high electron density of states at or in the close proximity of the Fermi level .…”