Modelling of structural and elastic changes of forsterite (Mg2SiO4) under stress |
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| Authors: | Michele Catti |
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| Institution: | 1. Dipartimento di Chimica Fisica ed Elettrochimica dell'Università, via Golgi 19, I-20133, Milano, taly
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| Abstract: | The method of crystal static deformation, including inner strain effects, was applied to calculate the structure configuration
and the elastic constants of forsterite under anisotropic and isotropic pressure. A Born type interatomic potential is used,
with optimized atomic charges and repulsive radii; SiO4 tetrahedra are approximated as rigid units. Computations were carried out in the range 1–8 GPa, with steps of 1 GPa, for
the three uniaxial stresses τ1, τ2, τ3 and for pressure p. By interpolation of results, interatomic distances and elastic tensor components are shown to depend quadratically on stress.
A non-linear behaviour generally appears above 4 GPa; the importance of inner strain and non-linear effects is analyzed. Mg-O
bond lengths and O-O edges of coordination polyhedra respond differently to anisotropic and to isotropic stresses, according
to the topological features of the structure. Elastic and structural results for hydrostatic pressure are compared to experimental
literature data, discussing the range of validity of the rigid body approximation for SiO4 groups. |
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