Kinetic instability and superconductivity in Li2AuH6 and Li2AgH6 at ambient pressure
Abstract
Li2AuH6 and Li2AgH6 have been proposed as promising candidates for high-temperature superconductors under ambient pressure. While previous studies confirm the dynamic stability of these two thermodynamically unstable systems, their kinetic stability against quantum and thermal fluctuations remains to be verified. In this work, we use path integral molecular dynamics simulations to examine the kinetic stability of Li2AuH6 and Li2AgH6 under ambient pressure. We find both compounds are kinetically unstable. Li2AgH6 undergoes lattice collapse, whereas Li2AuH6 retains a stable fluorite-type Li-Au sublattice, but hydrogen atoms partially dimerize into molecules and diffuse within the host lattice. Using the stochastic path-integral approach, which is a nonperturbative approach applicable to systems with diffusive atoms, we investigate the superconductivity of Li2AuH6 in this state. We predict a superconducting transition temperature of 22 K, well below earlier predictions, due to the low density of states at the Fermi level caused by the collapse of hydrogen sublattice and hydrogen dimerization.
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