Direct measurements of the constant-volume heat capacity of solid parahydrogen from 22.79 to 16.19<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">cm</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>/mole and the resulting equation of state

The constant-volume heat capacity of solid parahydrogen ($p\ensuremath{-}{\mathrm{H}}_{2}$) has been measured directly from below 4 K to the melting line for six molar volumes (22.787 to 16.19 ${\mathrm{cm}}^{3}$/mole). These data have been analyzed using the Mie-Gr\"uneisen equation of state (EOS) to give the volume and temperature dependence of the Gr\"uneisen parameter and the EOS for $p\ensuremath{-}{\mathrm{H}}_{2}$, as well as the volume dependence of the quadrupole-quadrupole interaction parameter for orthohydrogen impurities. Good agreement is found with earlier 4-K high-pressure compression data, and reasonable agreement with direct strain-gauge measurements of $P(V,T)$. The thermodynamic properties for solid $p\ensuremath{-}{\mathrm{H}}_{2}$ at $P=0$ are obtained by extrapolation to larger molar volumes, with the $T=0$, $P=0$ equilibrium volume given as 23.234 (\ifmmode\pm\else\textpm\fi{}0.05) ${\mathrm{cm}}^{3}$/mole and the triple-point volume of the solid as 23.48 (\ifmmode\pm\else\textpm\fi{}0.05) ${\mathrm{cm}}^{3}$/mole. The rather large temperature dependence of the Gr\"uneisen parameter which results from a comparison with high-pressure melting-line data is discussed in terms of an explicit temperature dependence of the lattice vibration spectrum. No indications were found for phase transitions in solid $p\ensuremath{-}{\mathrm{H}}_{2}$, nor for premelting anomalies.

Перевод пока недоступен