6533b7d0fe1ef96bd125b6f0

RESEARCH PRODUCT

X-ray-diffraction study of the crystal structures and orientational glass state ofAr1−x(N2)xsolid solutions

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Solid solutions of ${\mathrm{Ar}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$(${\mathrm{N}}_{2}$${)}_{\mathit{x}}$ have been investigated by x-ray powder diffraction in the range 0.5x1.0, 8T60 K, and under hydrostatic pressures up to 2200 bars. The structural hcp-cubic (Pa3) phase transition is identified as a martensitic transformation with a wide transformation hysteresis. For x0.8 and T30 K the solid solutions show the orientational glass state, which is characterized by a superposition of inhomogeneous and homogeneous lattice strains. The inhomogeneous component is described by the random-field model. The homogeneous component corresponds to an orthorhombic distortion of the hcp lattice. Two products of the Pa3 phase have been detected: an orientationally disordered fcc state and the high-pressure \ensuremath{\gamma} modification. It is concluded that the Pa3 phase and its products have no direct relevance to the orientational glass state. The analogies to the glasslike state of the mixed cyanides and of ortho-para-${\mathrm{H}}_{2}$ are worked out.