Two-electron Coulomb integral
= Two-electron Coulomb integral
{title2=$J_{pq}$}
The electrostatic repulsion integral $J_{pq}=\iint|\phi_p(1)|^2|\phi_q(2)|^2r_{12}^{-1}\,d1\,d2$ in <atomic units>. For a normalized hydrogenic 1s orbital of exponent $\zeta$, the same-orbital value is $5\zeta/8$. It is a two-electron integral, unlike a diagonal Hückel one-electron parameter.