Structure, structural evolution and Superconductivity of high pressure hydrogen-rich alloys

Pressure has an enormous effect in altering the structure, physical and chemical properties of matters. In general, for elemental metals, compression led to loosely bound valence electrons redistributed into the interstitial vacancies and often resulted in novel open 2-D and 3D structures. Incidentally, when mixed with H_2, which has an electronegativity similar to group 13 and 14 elements, charge transfer Zintl-Klemen type compounds can be formed. This phenomenon helps to explain the structural trend in hydrogen-rich alloys predicted by First Principle methods. Under suitable conditions, these alloys may even become superconductors and, in some cases, with very high critical temperature (T_c). Analysis of the functional derivative of Eliashberg spectral functions show that efficient electron-phonon coupling over the entire vibrational spectrum can be achieved on crystal structures when the stretch and bend vibrations of weakly linked hydrogen network atoms are strongly mixed.