Quantum and temperature effects on crystal structure of superhydride: A path integral molecular dynamics study

Abstract

By classical and path-integral molecular dynamics simulations, we study the pressure-temperature ($P$-$T$) phase diagram of LaH${}_{10}$ to clarify the impact of temperature and atomic zero-point motions. We calculate the XRD pattern and analyze the space group of the crystal structures. For 125 GPa $\le P\le$ 150 GPa and $T=300$ K, we show that a highly symmetric $Fm\bar{3}m$ structure, for which superconductivity is particularly favored, is stabilized only by the temperature effect. On the other hand, for $T=200$ K, the interplay between the temperature and quantum effects is crucial to realize the $Fm\bar{3}m$ structure. For $P=$100 GPa and $T=$300 K, we find that the system is close to the critical point of the structural phase transition between the $Fm\bar{3}m$ structure and those with lower symmetries.

6 pages, 6 figures

References in corpus (4)

• Observation of the Wigner-Huntington Transition to Solid Metallic Hydrogen
• Hydrogen sulphide at high pressure: a strongly-anharmonic phonon-mediated superconductor
• Dissociation of high-pressure solid molecular hydrogen: Quantum Monte Carlo and anharmonic vibrational study
• Phonon-mediated high-temperature superconductivity in ternary borohydride KB${}_2$H${}_8$ around 12 GPa