Dislocation pipe radius for diffusion and the distribution are analyzed using combined an equivalent boundary slab model and a dislocation pipe model. Both models were applied to oxygen self-diffusion in MgO single crystal. The lattice diffusion coefficient D^l and the diffusion coefficient for oxygen diffusion along a dislocation, D^d, at 1350°C are obtained as D^l=1.17×10⁻²⁰ and D^d=4.44×10⁻¹⁶ m²sec⁻¹, respectively. Oxygen diffusion along the dislocation takes place within a pipe of radius 0.18 nm surrounding the dislocation. The theoretical results of dislocation structures, dislocation density d=3.2×10¹⁴ m⁻² and subgrain size b=1.15 mum, are found to agree well with the electron-microscopic experiments by Moriyoshi and Ikegami (1985).

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The electron-density distribution in a crystal of FeTiO₃ has been investigated by means of the single crystal X-ray diffraction method. A small amount of partial disorder was observed in the cation arrangement of the examined crystal. The crystal has the cell dimensions a=5.08854(7), c=14.0924(3) Å, with the space group R-3, Z=6, D_x=4.789 g cm⁻³, and μ(Mok α)=103.40 cm⁻¹. Residual electron densities observed around the Fe²⁺ ion after refinement based on the spherical atom model are qualitatively explained with a configuration of 3d electrons near the high-spin state. Population analysis with the assumption of the 3(C₃) crystal field yielded the electron populations of 1.31, 2.33, and 2.36 for the a, e(t_2g) and e(e_g) orbitals, respectively. The subsequent refinement with anharmonic thermal parameters for cations markedly reduced the residual densities around Fe²⁺ ion.

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Mössbauer spectra of a ferric-diopside DI₇₅FE₂₅ (DI=CaMgSi₂O₆, FE=CaFe³+Fe³⁺SiO₆) have been measured at 78K and 4.2K. Although the magnetic transition from a paramagnetic to antiferromagnetic state did not occur above 78K, about 60% of ferric irons in both 4-(Ts) and 6-coordinated (Ml) sites were transformed to an antiferromagnetic state at 4.2K. These magnetic parts in the diopside structure have the following Mössbauer parameters: isomer shift=0.19mm/s relative to iron metal, quadrupole splitting=0.27mm/s, line width 1.4-2.4mm/s and internal magnetic field=375kG. Unusual broad line width and weak magnetic field show that these parts may be formed as the clusters of adjacent coordination sites Ts and M1 preferentially occupied by ferric irons. About 30% of ferric irons were retained equally at both sites as a paramagnetic state even at 4.2K, judging from the absorption area ratios of two quadrupole doublets.

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This is the final report on the nomenclature of pyroxenes by the Subcommittee on Pyroxenes established by the Commission on New Minerals and Mineral Names of the International Association. The recommendations of the Subcommittee as put forward in this report have been formally accepted by the Commision. Accepted and widely used names have been chemically defined, by combining new and conventional methods, to agree as far as possible with the consensus of present use. Twenty names are formally accepted, among which thirteen are used to represent the end-members of definite chemical compositions. In common binary solid-solution series, species names are given to the two end-members by the “50% rule”. Adjectival modifiers for pyroxene mineral names are defined to indicate unusual amounts of chemical constituents. This report includes a list of 105 previously used pyroxene names that have been formally discarded by the Commision.

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