Order‐Disorder Phenomena. VII. Critical Variations in the Length of NH4Cl Single Crystals at High Pressures

摘要: A high‐precision capacitance method has been used to investigate variations in the length L of an NH4Cl single crystal vicinity its order—disorder transition line. At low pressures, there is a small first‐order discontinuity ΔL superimposed on lambdalike variation L. 255.95°K and 1491.8 bar, varies continuously but κT α appear diverge. higher at becomes progressively more gradual as pressure increases. The linear isothermal compressibility immediate well represented along isotherm by κ = (κ lim ∼L + B φ −y) / (1 2 pB −y), where ≡ |  p−p c  | /  p c pc for given isotherm. quantity κL assigned constant value 1.57 × 10−6bar−1 all isotherms; y (which are assumed be independent pressure) vary with temperature. isobaric coefficient thermal expansion fairly isobar =...