Question

at low temprature hydrogen is which type of molecular solid

Answer 1

At low temperatures and at pressures up to around 400 GPa, hydrogen forms a series of solid phases formed from discrete H2 molecules. Phase I occurs at low temperatures and pressures, and consists of a hexagonal close-packed array of freely rotating H2 molecules. Upon increasing the pressure at low temperature, a transition to Phase II occurs at up to 110 GPa. Phase II is a broken-symmetry structure in which the H2 molecules are no longer able to rotate freely. If the pressure is further increased at low temperature, a Phase III is encountered at about 160 GPa. Upon increasing the temperature, a transition to a Phase IV occurs at a temperature of a few hundred kelvin at a range of pressures above 220 GPa.