Quantum and Anharmonic Effects in Superconducting <i>Im</i>3<i>m</i> CaH₆ Under High Pressure: A First-Principles Study

Abstract

Clathrate hydrides have attracted much attention in recent years as superconductors that are most likely to achieve room-temperature superconductivity. As the first nontransition metal clathrate hydrides successfully synthesized in experiments, CaH6 provides a great reference value for the study of superconductivity in hydrides. However, the difference between the experimental measurement and the theoretical prediction of its Tc is an important issue that cannot be ignored. Solving the self-consistent harmonic approximation by a stochastic approach, we could introduce the anharmonic correction to resolve the discrepancy between the theoretical prediction and experimental observation of Tc of CaH6. We also proposed a scheme to correct the deformation potential to calculate the electron–phonon interaction more accurately. We found that by introducing anharmonic effect and modifying the deformation potential, the experimental results can be well matched, and the problem of differences between theoretical predictions and experimental observations can be solved. Our results represented that the anharmonicity may be one way to solve the difference between the experimental and theoretical results.