Pressure-Stabilized Superconductive Ionic Tantalum Hydrides

Abstract

High-pressure structures of tantalum hydrides were investigated over a wide pressure range of 0-300 GPa by utilizing evolutionary structure searches. TaH and TaH₂ were found to be thermodynamically stable over this entire pressure range, whereas TaH₃, TaH₄, and TaH₆ become thermodynamically stable at pressures greater than 50 GPa. The dense Pnma (TaH₂), R3̅m (TaH₄), and Fdd2 (TaH₆) compounds possess metallic character with a strong ionic feature. For the highly hydrogen-rich phase of Fdd2 (TaH₆), a calculation of electron-phonon coupling reveals the potential high-T_c superconductivity with an estimated value of 124.2-135.8 K.