Here, all two-electron integrals (1/r_{12}) are computed. As they have 4 indices and many are zero, they are stored in a map, as defined in :file:`utils/map_module.f90`.
To fetch an |AO| integral, use the get_ao_two_e_integral(i,j,k,l,ao_integrals_map) function.
The conventions are: * For |AO| integrals : (ij|kl) = (11|22) = <ik|jl> = <12|12>