Refinement of the structure of rankinite.

Abstract

The crystal structure of rankinite (Ca3Si2O7) was refined to an R value of 0.033 by full matrix least-squares using 1492 three-dimensional counter-measured intensity data. The crystal is monoclinic, P21⁄a, with a=10.557(1) Å, b=8.885(3) Å, c=7.858(1) Å, β=119.586(6)°, Z=4. The coordination polyhedra of calcium atoms form sheeets parallel to the (010) plane, between which Si2O7 groups are inserted. The lengths of Si–O bridge bonds are longer than those of non-bridge bonds. Listings are given of newly obtained bond lengths and bond angles of the structures.