Bueble, S.; Schmahl, Wolfgang W.
Mechanical twinning in calcite considered with the concept of ferroelasticity.
In: Physics and Chemistry of Minerals, Vol. 26, Nr. 8: S. 668-672
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The mechanical twinning of calcite is compared with ferroelastic behavior. For calcite a paraelastic prototype phase does not exist, therefore a virtual prototype is defined with cubic m3m symmetry. Using this condition the strain tensors of all domain states of mechanical twinning are calculated. With the use of the strain tensors, application of Sapriel’s strain compatibility law gives the crystallographic orientations of all possible twin planes between different domain states. The findings indicate that the twin walls are 1 0 0 and 1 1 0 planes with respect to the morphological rhombohedral lattice. These twin plane orientations from the equated strain tensors are in accordance with the r-and e-twin systems commonly observed in calcite.