Neutron powder diffraction study of the orientational order–disorder phase transition in calcite, CaCO3
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- Dove, M.T., Swainson, I.P., Powell, B.M. et al. Phys Chem Minerals (2005) 32: 493. doi:10.1007/s00269-005-0026-1
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Neutron powder diffraction studies of calcite on heating towards the orientational order–disorder phase transition show that the phase transition is not a simple analogue of an Ising-like transition, but more similar to a rotational analogue of Lindemann melting. The transition is precipitated by the librational amplitude of the carbonate molecular ions exceeding a critical value rather than a result of a statistical entropy of ‘wrong’ orientations. Using tested interatomic potentials the single-particle orientational potential and nearest-neighbour orientational interactions have been calculated.