Reciprocal Cell Axes

The three reciprocal cell axes of a crystallographic unit cell are termed a*, b* and c* and lie in the following directions:

a* is perpendicular to the real cell axes b and c;
b* is perpendicular to the real cell axes a and c;
c* is perpendicular to the real cell axes a and b.

Thus, if you view a structure down a*, you are looking in a direction normal to the bc plane of the unit cell. A reciprocal and real cell axis may be coincident, but only if the symmetry of the crystal requires that the relevant cell angles are 90 degrees. For example, in a monoclinic crystal with the b axis unique, the cell angles alpha and gamma are required by symmetry to be 90 degrees, so the real axis b and the reciprocal axis b* will lie along the same direction.

Relevant Program Options:

Viewing along reciprocal cell axes (see Section 5.5)

Related Topics

Crystal System
Unit Cell

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