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GEO‐MIX‐SELF calculations of the elastic properties of a textured graphite sample at different hydrostatic pressures
Author(s) -
Matthies Siegfried
Publication year - 2012
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s002188981104338x
Subject(s) - graphite , materials science , anisotropy , texture (cosmology) , hydrostatic pressure , crystallite , hydrostatic equilibrium , volume (thermodynamics) , orientation (vector space) , condensed matter physics , composite material , mechanics , thermodynamics , optics , geometry , physics , mathematics , metallurgy , image (mathematics) , quantum mechanics , artificial intelligence , computer science
The recently developed GEO‐MIX‐SELF approximation (GMS) is applied to interpret the pressure dependence of the longitudinal ultrasonic wave velocities in a polycrystalline graphite sample that has already been investigated in a wide range of experimental contexts. Graphite single crystals have extremely anisotropic elastic properties, making this sample a challenging test to demonstrate the potential of the GMS method. GMS combines elements of well known self‐consistent algorithms and of the geometric mean approximation. It is able to consider mixtures of different polycrystalline phases, each with its own nonspherical grain shape and preferred orientation (texture). Pores and `cracks', typical for bulk graphite, are modeled as phases with `empty' grains. The pressure dependence (up to 150 MPa) of the experimental wave velocities can be well explained using the known texture of the sample by fitting the shape parameters and volume fractions of the graphite grains, cracks and spherical pores. The pressure dependence of these parameters describes a reasonable scenario for the closing of the cracks and pores with increasing pressure.