Padé-approximant study of the phase transition of ortho–para mixtures in solid hydrogen

Abstract

The phase transition of solid hydrogen is studied in the Padé approximation, with newly calculated coefficients in the high-temperature expansion series for the free energy. For the low-temperature phase, the free energy is obtained by a previous libron study of ortho–para mixtures. The transition temperature is predicted to be 2.1Γ for pure ortho-hydrogen. The phase transition disappears at ~ 60% of ortho-hydrogen, in agreement with experiment.