Anharmonic and kinetic effects on the stabilization pressure of high-T_cclathrate hydrides

We recently reported the theoretical prediction of novel high-performing clathrate hydride superconductors, such as LaBH₈, SrSiH₈, and BaSiH₈. Within harmonic phonon calculations, we determined the minimum pressures of dynamical stability in these clathrates to be below 40 GPa, while retaining the superconducting state up to temperatures in the order of 100 K.

This talk focuses on the effects of vibrational zero-point energy, phonon anharmonicity and kinetic enthalpy barriers on the stabilization pressure of the high-symmetry phases, using in particular the example of BaSiH₈, where we determined dynamic stability at 5 GPa. The explicit calculation of the enthalpy barriers protecting the structure from decomposition yields a kinetic pressure threshold that is sensibly higher than the one based on dynamic stability, but gives a much more rigorous limit for synthesizability.