Thank you for your reply.
This is one of the things which I've been trying to do. However I end up with a result which is a very complicated integral. Expanding the difference of the length of the two vectors gives:
|\vec{r}_1 - \vec{r}_2| = \sqrt{r_1^2 + r_2^2 - 2r_1 r_2 \cos\beta} Where...
Hello. I need to find the expectational value of the correlation energy between two electrons which repel each other via the classical Coulomb interaction. This is given by the 6-dimensional integral:
\left\langle\frac{1}{|\vec{r}_1 - \vec{r}_2|}\right\rangle...