The plateau effect in thermal conductivity of solid hydrogen with neon impurity

The thermal conductivity of solid hydrogen with 1–2 ppm Ne impurity was investigated in the temperature range 1.5–10 K on samples grown from the liquid phase at various growth rates. The result differ qualitatively from those obtained on samples grown from the gas phase: the thermal conductivity curve exhibited a dip in a broad plateau. The relaxation model is suggested to explain the effect supposedly due to linear impurity structures, arranged on dislocation lines. A comparison with the case of isolated neon atoms homogeneous distributed in the solid hydrogen is made

Diffusion model of the thermal conductivity plateau of weak solid solutions of neon in parahydrogen

The diffusion kinetic of classic impurity particles has been investigated in the frame of one-dimensional two-level model and applied for the explanation of solid hydrogen thermal conductivity data with extremely low con-centrations of neon impurity in samples growth at different crystallization rates in which the plateau effect was observed. The main idea is that heavy isotopic impurities could segregate into thin long chains near dislocation cores if the growth rate is slow. Neon impurity chains can persist for a long time. Such rigid linear objects ensure inelastic scattering of phonons. The diffusion coefficient of neon atoms in (p-H₂)₁–cNec mixtures was estimated for the experimental conditions with с = 0.0001 аt. % and с = 0.0002 аt. %

Influence of rotational motion of molecules on the thermal conductivity of solid SF₆, CHCl₃, C₆H₆, and CCl₄

The thermal conductivity of solid SF₆, CHCI₃, C₆H₆, and CCl₄ was investigated by the linear-flow method under saturated vapor pressures in the temperature range from 80 K to the corresponding melting temperatures and then recalculated for a constant density of the samples. The contributions of the phonon–phonon and phonon–rotation interactions to the total thermal resistance were separated using the modified method of reduced coordinates. It is shown that the phonon–rotation contribution to the thermal resistance of the crystals decreases as the rotational motion of the molecules attains more freedom

Role of the orientational subsystem in the expansion of pure CF₆, CHCl₃, C₆H₆, CCl₄ and N₂O with Kr impurity

The linear expansion coefficients of solid bulk samples of N₂O with Kr 5% impurity are measured by an absolute dilatometric method in comparison with pure N₂O in the temperature range 80–150 K. An additional unusual orientational effect is discussed. An analysis of the data from measurements of the linear expansion coefficients of pure solid SF₆, CHCl₃,C₆H₆, CCl₄ in comparison with solid Xe in the temperature range 80–170 K is carried out in order to determine the role of molecules` orientational disordering in the thermal expansion of the given condensed systems. The results are discussed in connection with the problem of determining the contribution of orientational subsystems with different types of molecular symmetry to the total thermal expansion and its behavior in various temperature intervals of solid phase existence