Possible Point of Confusion - Centered Cells and Centers of Inversion

"Centered" cells and centers of inversion? This is one of a few unfortunate semantic and nomenclature problems that students just have to get used to before becoming members of the Guild. Centered cells are ones with multiple lattice points per cell. The symmetry operations associated with them all involve translations of 1/2 along various directions in the cell. For example, a C-centered cell involves a translation of (1/2,1/2,0) while an I- centered cell includes a translation of (1/2,1/2,/1,2). The words "center" and "centrosymmetric" are associated with centers of inversion. With practice, it'll be easy to use the context of what you're reading or hearing to tell the difference between "centering" and inversion centers.

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copyright © Ron Stenkamp stenkamp@u.washington.edu Most recent update 1/7/97