A refined technique for measuring crystal size distributions in thin section

Article Abstract:

Computer experiments, involving the preparation of 2-dimensional (2D) sections from 3-dimensional (3D) solids, allow the measurement of the 3D log-normal crystal size distributions (CSD) in thin sections. An exact correction for spheres of uniform diameter forms the basis for the 2D to 3D conversion. The study of igneous phenocrysts shows that strongly oriented textures can be correctly measured by this method. The technique has been successfully implemented for CSDs modified by megacryst retention, xenocryst addition, and groundmass nucleation in alkaline rocks and a kimberlite.

Crystal structure, Computer simulation

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Water-related defects and oxygen diffusion in albite: a computer simulation study

Article Abstract:

Computer simulation methods facilitate the study of the energetics of the formation of water-related defects and the estimation of oxygen diffusivity in albite. Formation energy is lowest for the Na Frenkel defect. The most favorable oxygen defects are the impurity-related interstitials. The albite structure can accommodate water in the form of OH groups and as H2O molecules. Activation energies for the migration of O experience a 50% reduction when O migrates as part of OH group. The activation energy is dependent on the diffusion direction.

Research, Oxygen, Diffusion, Diffusion (Physics), Plagioclase

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Monte Carlo simulation of normal grain growth in 2- and 3-dimensions: the lattice-model-independent grain size distribution

Article Abstract:

Monte Carlo simulations were done on single-phase crystals to determine the normal grain growth in 2- and 3-dimensions. The undesirable coalescence and anisotropic effects have been excluded in these simulations. The study shows that the resulting grain size distribution has the universal form consistent with real normal grain growth. These findings are consistent with empirical rock data.

Analysis, Growth, Monte Carlo method, Monte Carlo methods, Crystal growth

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