${\mathrm{Li}}_2{\mathrm{AuH}}_6$ and ${\mathrm{Li}}_2{\mathrm{AgH}}_6$ 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 ${\mathrm{Li}}_2{\mathrm{AuH}}_6$ and ${\mathrm{Li}}_2{\mathrm{AgH}}_6$ under ambient pressure. We find both compounds are kinetically unstable. ${\mathrm{Li}}_2{\mathrm{AgH}}_6$ undergoes lattice collapse, whereas ${\mathrm{Li}}_2{\mathrm{AuH}}_6$ 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 ${\mathrm{Li}}_2{\mathrm{AuH}}_6$ 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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• Superconductivity
• Hydrides
• Ab initio molecular dynamics
• Bethe-Salpeter equation
• Eliashberg theory
• First-principles calculations
• Path integrals