Specific heat of solid nitrogen-argon mixtures: 50 to 100 mol%<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">N</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

We have measured the specific heat, ${C}_{p}$, of solid ${\mathrm{N}}_{2}$-argon alloys of 49.75, 62.83, 70.43, 79.85, and 100 mol% ${\mathrm{N}}_{2}$ concentration between 4.5 and 40 K. The measurements were made to investigate the possible formation of a rotational glass phase similar to that of solid ${\mathrm{H}}_{2}$. The three lower-concentration samples showed no evidence of a sharp transition to a glass phase nor any thermal remanence indicative of a glass, although the rotational contribution to the specific heat was qualitatively similar to that of the solid ${\mathrm{H}}_{2}$ glass. The 49.75-mol% sample did not exhibit the martensitic hcp-to-fcc crystalline transition expected at 23 K, indicating that cold working is important to forcing this transition. The $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\beta}$ phase transition in pure ${\mathrm{N}}_{2}$ was very sharp upon cooling to the transition point, without any pretransitional effects, whereas the $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\beta}$ transition in the 79.85-mol% sample had a $\ensuremath{\lambda}$-like appearance.

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