Swainson, I.P.; Dove, M. T.; Schmahl, Wolfgang W.; Putnis, A.
Neutron powder diffraction study of the åkermanite-gehlenite solid solution series.
In: Physics and Chemistry of Minerals, Vol. 19, Nr. 3: S. 185-195
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The crystal structures of members of the åkermanite-gehlenite solid solution series have been refined from high resolution neutron powder diffraction data. Synthetic samples of 0, 25, 50, 75 and 100\% åkermanite composition were used. The results are consistent with the ordering scheme for the tetrahedrally-coordinated cations represented by the structural formula Ca2[MgxAl1-x]1[Si1+x Al1-x]2O7 where the superscripts denote inequivalent tetrahedral sites. No evidence was found for the existence of phase transitions in the samples with x ≤ 0.75, in contrast to the behaviour found in pure åkermanite. The relationship between the cell parameters of meilite and the tetrahedral conformations and the resulting non-ideality of the solid-solution are discussed.