Computer Simulation of a Microstructure in a Potassium Feldspar

I. Tsatskis* and E. K. H. Salje1, 2
1 Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
2 Interdisciplinary Research Centre in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK
*Previous name: I. V. Masanskii

Abstract: Kinetics of atomic ordering in a potassium feldspar is simulated using massively parallel computing. The simulation method is based on the Monte Carlo algorithm for the Al-Si redistribution (the Kawasaki dynamics) combined with the lattice relaxation. The Hamiltonian has the symbolic form H=12uAu−uFp where u represents displacements of atoms from ideal positions, and p the Al and Si occupation numbers. The model is purely elastic; there is no direct interaction between Al and Si atoms. The simulated crystal is a thin film with (010) surfaces and consists of 64 × 64 unit cells; the unit cell defined for the whole film contains slightly more than 4 formula units. The (010) orientation is chosen in order to preserve in the film the main structural feature of feldspars: crankshaft-like sheets formed by four-tetrahedra rings. This makes it possible to observe the Pericline twins only. At the late stage of the kinetic run these twins are clearly seen. The direction for the domain walls is determined by the spontaneous strain and changes with the change of the model parameters; considerable local deviations from this direction are observed.

Keywords: feldspar • microstructure • phase transition • kinetics • domains

Mineralogical Magazine; December 1995 v. 59; no. 397; p. 623-628; DOI: 10.1180/minmag.1995.059.397.06
© 1995, The Mineralogical Society
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