InternationalReciprocal spaceTables for Crystallography Volume B Edited by U. Shmueli © International Union of Crystallography 2010 |
International Tables for Crystallography (2010). Vol. B, ch. 1.2, p. 22
## Section 1.2.13. The generalized structure factor |

In the generalized structure-factor formalism developed by Dawson (1975), the complex nature of both the atomic scattering factor and the generalized temperature factor are taken into account. We write for the atomic scattering factor: and where the subscripts c and a refer to the centrosymmetric and noncentrosymmetric components of the underlying electron distribution, respectively. Substitution in (1.2.4.2) gives for the real and imaginary components *A* and *B* of and (McIntyre *et al.,* 1980; Dawson, 1967).

Expressions (1.2.13.3) illustrate the relation between valence-density anisotropy and anisotropy of thermal motion.

### References

Dawson, B. (1967).*A general structure factor formalism for interpreting accurate X-ray and neutron diffraction data. Proc. R. Soc. London Ser. A*,

**248**, 235–288.

Dawson, B. (1975).

*Studies of atomic charge density by X-ray and neutron diffraction – a perspective*. In

*Advances in Structure Research by Diffraction Methods.*Vol. 6, edited by W. Hoppe & R. Mason. Oxford: Pergamon Press.

McIntyre, G. J., Moss, G. & Barnea, Z. (1980).

*Anharmonic temperature factors of zinc selenide determined by X-ray diffraction from an extended-face crystal. Acta Cryst.*A

**36**, 482–490.