Crystal chemistry and structure refinement of five hydrated calcium borates

The crystal structures of the five known members of the series Ca₂B₆O₁₁·xH₂O (x = 1, 5, 5, 7, 9, and 13) have been refined by full-matrix least-squares techniques, yielding bond distances and angles with standard errors of less than 0·01 Å and 0·5°, respectively. The results illustrate the crystal chemical principles that govern the structures of hydrated borate compounds. The importance of hydrogen bonding in the ferroelectric transition of colemanite is confirmed by more accurate proton assignments.