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

The phase transition of solid hydrogen is studied in the Pade 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. (4 refs., 3 figs.)