The crystal structure of manandonite-2H2, an Al-, Li-, B-rich analogue of amesite, has been refined in space group C1 to R = 5.7%. Tetrahedral Si, Al, and B are partly ordered to give two mean T-O bond lengths near 1.603(1) Å and two near 1.667(1) Å. B has a greater tendency to order than do Si and Al. There are one relatively Li-rich octahedron and two relatively Al-rich octahedra in each layer with mean M-0,0H bond lengths of 1.997(1), 1.960(1), and 1.955(1) Å, respectively, in layer 1 and 2.014(1), 1.941(1), and 1.956(1) Å, respectively, in layer 2. It is the partial ordering of the octahedral cations that decreases the ideal P63 symmetry to P1 (or C1, as used for refinement). Tetrahedral rotations of 18.3° are required to match the larger lateral dimensions of the tetrahedral sheet with those of the octahedral sheet, coupled with basal O corrugations because of the different sizes of the octahedra. The H+ protons of the six surface OH molecules point directly toward their acceptor basal O atoms to give H bond contacts between 2.647 and 2.773 Å.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.