The Book of Crystallography

An atom, and its Fourier Transform:

Note the both functions have circular symmetry. The atom is a sharp feature, whereas its transform is a broad smooth function. This illustrates the reciprocal relationship between a function and its Fourier transform.

A molecule, and its Fourier Transform:

The molecule consists of seven atoms. Its transform shows some detail, but the overall shape is still that of the atomic transform. We can consider the molecule as the convolution of the point atom structure and the atomic shape. Thus its transform is the product of the point atom transform and the atomic transform.

More Fourier transforms. Back to the index.