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The structure and microplasticity of high-purity fullerite C60 have been investigated comprehensively. The crystalline structure, lattice parameters, and phase transitions have been studied by x-ray diffractometry in the temperature range 30–293 K. It is found that the temperature corresponding to the orientational order–disorder phase transition is Tc=260 K. A considerable number of regions with stacking faults discovered in the samples leads to blurring of the fcc→sc phase transition in the temperature interval Tc±3 K. The a(T) dependences of the lattice parameter display peculiarities at the following characteristic temperatures: Tc at which the lattice parameter jump Δa/a=3.3×10−3 is observed, and the temperatures T0≃155 K, and Tg≃95 K which are associated with the beginning and end of molecular orientation freezing. It is shown that the formation of orientational glass is accompanied by a considerable increase in the width of x-ray reflections. The slip geometry and the temperature dependence of microhardness HV are studied in the temperature interval 81–293 K. It is shown that a system of the {111}〈110〉 type is the only slip system in the fcc and sc phases. The value of HV depends on the indentation plane: HV111>HV100. Below Tc, the microhardness increases abruptly (by approximately 30%). The temperature interval of this anomaly decreases after annealing of the crystal in vacuum. At T<T0, the HV(T) dependence becomes much stronger. It is shown that the hardness of C60 normalized to the elastic shear modulus is higher than the hardness of typical molecular crystals at comparable homologic temperatures.

The weak magnetic polarization which a quantum vortex in a superfluid Bose liquid acquires as a result of the mutual electric polarization of atoms and the nonuniform distribution of the atomic density in its core is discussed. A rectilinear single-quantum vortex carries a magnetic moment directed along and proportional to the length of the vortex line. The magnetic moment density per unit length and the corresponding quantum of magnetic flux (vortex fluxoid) are directly related with the quantum circulation of the superfluid flow in the vortex. Numerical estimates of this effect are presented for vortices in He II.

In honour of Professor V. I. STARTSEV'S 70th birthday The rearrangement of the force of dynamic dragging of a dislocation due t o its elastic interaction with impnrity atoms is analysed. The collisions of a moving dislocation with impurities excite additional vibrations of a dislocation line. Such vibrations lead to tho appearance of extra parts to dissipative function and effective friction force of a dislocation which dcperid on location and concentration of impurities. This effect is one of tho reasons of the influence of impiiritics observed in the expcriments on the dynamic branch of the moving didocation curve.

The vortical motion of atoms in a quantum liquid is accompanied by their weak polarization under the action of centrifugal forces. Theoretical estimates of the effect give an electric field close to the axis of the vortex of about 300 V⋅cm−1 and a linear density of the bound charge in the core of about (3e)cm−1 (e is the charge of an electron).

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The results of research on the plasticity and strength of a wide class of metal oxide perovskite-like compounds which have the property of high-temperature superconductivity or which can be used as base compounds for making high-temperature superconductors (HTSCs) are systematized and presented from a unified point of view. The mechanical properties of materials with different morphology—single crystals, polycrystals, and composites,—measured by different methods of mechanical testing in the low-temperature, room-temperature, and high-temperature regions, are discussed. The characteristic defects of the crystal structure for these compounds are considered, the crystallography of two modes of plastic deformation—slip and twinning—is described, and the stress-induced structural rearrangement of the twin structure that appears at a high-temperature phase transformation is discussed. The features of plastic deformation and fracture of metal oxide materials due to structural microdefects (dislocations, impurities, twin and grain boundaries) and macrodefects (voids, cracks, heterophase inclusions) are noted, and the role of heavy-cation diffusion in the kinetics of high-temperature deformation is discussed. The influence of structural phase transformations and the superconducting transition on the mechanical properties of metal oxides is considered. This review is a continuation of a review of the elastic and acoustic properties of HTSCs published earlier by the authors in Fiz. Nizk. Temp. 21, 475 (1995) [Low Temp. Phys. 21, 367 (1995)].

The creep of β-Sn single crystals oriented for slip in the (100)〈010〉 system is investigated in the temperature range 0.45–4.2 K. A transient creep, decaying in time by a logarithmic law, is registered both above and below 1 K. The temperature dependence of the coefficient of logarithmic creep is studied in detail, and the existence of two qualitatively different regions of its behavior is established: in the interval 4.2–1.2 K the coefficient increases linearly with decreasing temperature, while below 1 K the creep acquires an athermal character and the coefficient remains constant. It is shown that the regularities observed in the experiment are in accord with the idea that the kinetics of creep in pure β-Sn is governed by the motion of dislocations in the Peierls potential relief by a mechanism of nucleation of kink pairs on the dislocation lines. This process entails the overcoming of a small effective potential barrier of the order of 0.001 eV: in the temperature region T<1 K the nucleation of kink pairs occurs by a quantum tunneling effect, and the creep is of a purely quantum character; at higher temperatures the leading role is played by thermal fluctuations, and the deformation kinetics corresponds to the classical ideas of thermally activated creep. Empirical estimates are obtained for the density of mobile dislocations and the work hardening coefficient.