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.