Polyhydride

[1] Polyhydrides are important because they can form substances with a very high density of hydrogen.

These are formed at 30 GPa and 2,100 K.[2] Heating and compressing a metal with ammonia borane avoids using bulky hydrogen, and produces boron nitride as a decomposition product in addition to the polyhydride.

There should also be electron-phonon coupling which happens when the electric properties are tied to the mechanical position of the hydrogen atoms.

[35][50][51] The highest superconduction critical temperatures are predicted to be in groups 3 and 3 of the periodic table.

Late transitions elements, heavy lanthanides or actinides have extra d- or f-electrons that interfere with superconductivity.

[52] For example, lithium hexahydride is predicted to lose all electrical resistance below 38 K at a pressure of 150 GPa.

PH3 doped H3S is also predicted to have a transition temperature above the 203 K measured for H3S (contaminated with solid sulfur).

[56] H3Se actually is a van der Waals solid with formula 2H2Se·H2 with a measured Tc of 105 K under a pressure of 135 GPa.

Unit cell diagram showing the structure of NaH 7 , which contains H − 3 complexes. The coloured balls in the isosurface, plotted at the level of 0.07 electrons*Å −3 . One of H 2 molecules is bonded to a hydrogen atom in the NaH unit with a bond length of 1.25 Å, forming a H − 3 linear anion.