### Abstract

In a previous paper we considered the function χ(**r**) ≡ (1/*N*) **Σ**_{k} *e* ^{ i k·r }, where the sum runs over the first Brillouin zone of a crystal, and its expansion into series of Cubic Harmonics . Houston's method was used in order to find the radial functions *g*_{j} (*r*) for several values of *j*, for χ(**r**) given for the simple cubic and the face‐centered cubic lattices. In this paper, the same considerations are applied to χ(**r**) given for the body‐centered lattice. *g*_{j} (*r*), with *j* = 0, 2, 3, are calculated in the region of small *r* which is assumed as 0 ≤ *r* ≤ 2*a*, where *a* is the lattice constant. In most of the problems of solid‐state physics, where the function χ(**r**) occurs, it is satisfactory to know its values only for small *r*, usually not larger than 2*a*. The function *g* _{0}(*r*) is calculated using 3‐, 6‐, and 9‐term expansion formulas, *g* _{2}(*r*) and *g* _{3}(*r*) using only 3‐ and 6‐term formulas. Comparing *g*_{j} (*r*) obtained from the formulas with different number of terms it is established that, for *r* in the region 〈0, 2*a*〉, the 6‐term approximation is very good.