FWF - SuperHydra - SuperHydra

Superhydrides, i.e. hydrides with a ultra-high hydrogen content, have been predicted at planetary pressures, and recently observed in several binary systems, such as Li-H, Al-H, Na-H, etc. In 2014, one of these compounds, SH3, broke the record for superconducting critical temperatures (Tc) previously held by the cuprates, setting the bar at 203 K. High-Tc superconductivity in metallic superhydrides is expected on the basis of conventional Migdal-Eliashberg theory, due to the high phonon frequencies involved in the superconducting pairing. At the same time, superhydrides are also attractive for hydrogen storage applications, because they permit to realize relative hydrogen densities much higher than current hydrogen storage materials. The high pressure needed to stabilize these phases is an obvious limitation to their practical use. However, a recent report of superconductivity in PdH with Tc of 61 K at ambient pressure upon cold compression, suggests that some superhydrides phases could be quenched down to ambient conditions, making their study attractive also for prospective technological applications. In this project we employ ab-initio methods for crystal structure prediction, thermodynamics and superconductivity, to study the high-pressure phase diagrams up to the multi-Megabar range of three classes hydrides: metal hydrides, covalent (molecular) hydrides, and covalent-ionic hydrides, commonly used for hydrogen-storage applications. Our main goal is to identify new high-Tc superconducting phases at high pressures and metastable H-rich phases which could be quenched down to ambient pressure for superconductivity or hydrogen-storage applications. The project will have a big impact on fundamental research, as the behavior of H-rich solids at high pressures is currently object of intense investigation. Furthermore, three types of predictions, which may be verified within the proposed time-frame, would have a transformative impact: (i) a high-Tc, superconductor at ambient pressure; (ii) a new superhydride phase, with performances comparable to the best current hydrogen-storage materials; (iii) a room temperature superconductor at high pressures. The PI has entered the field of high-pressure superconductivity immediately after the discovery of SH3. This, together with her proven record of collaboration with experimental groups, will ensure an excellent visibility for the project, the possibility of testing the theoretical predictions, and an optimal dissemination of the results.