Temperature and quantum anharmonic lattice effects on stability and superconductivity in lutetium trihydride.

In this work, we resolve conflicting experimental and theoretical findings related to the dynamical stability and superconducting properties of [Formula: see text]-LuH, which was recently suggested as the parent phase harboring room-temperature superconductivity at near-ambient pressures. Including temperature and quantum anharmonic lattice effects in our calculations, we demonstrate that the theoretically predicted structural instability of the [Formula: see text] phase near ambient pressures is suppressed for temperatures above 200 K. We provide a p-T phase diagram for stability up to pressures of 6 GPa, where the required temperature for stability is reduced to T > 80 K.

Quantum lattice dynamics and their importance in ternary superhydride clathrates.

The quantum nature of the hydrogen lattice in superconducting hydrides can have crucial effects on the material's properties. Taking a detailed look at the dynamic stability of the recently predicted BaSiH phase, we find that the inclusion of anharmonic quantum ionic effects leads to an increase in the critical dynamical pressure to 20 GPa as compared to 5 GPa within the harmonic approximation. We identify the change in the crystal structure due to quantum ionic effects to be the main driving force for this increase and demonstrate that this can already be understood at the harmonic level by considering zero-point energy corrections to the total electronic energy.

Superconductivity and strong anharmonicity in novel Nb-S phases.

In this work we explore the phase diagram of the binary Nb-S system from ambient pressures up to 250 GPa usingevolutionary crystal structure prediction. We find several new stable compositions and phases, especially in the high-pressure regime, and investigate their electronic, vibrational, and superconducting properties. Our calculations show that all materials, besides the low-pressure phases of pure sulfur, are metals with low electron-phonon (ep) coupling strengths and critical superconducting temperatures below 15 K.