Do any freely available or proprietary electronic structure packages explicitly compute two-electron exchange correlation integrals?
I have found a few derivations to calculate excited state properties/spectroscopic observables using DFT, and they tend to write expressions including integrals of the form
where $w$ is the exchange-correlation kernel. However, I have yet to find a package that specifically generates these integrals. It seems that in general they do some sort of prior contraction with the density to avoid the need to generate these terms explicitly when calculating response properties. However, I had wanted to make a small standalone script that used these quantities. Its presumably much less efficient than the approach used in these packages, but the implementation is much clearer for me. Are there any packages that have an existing option to do this? Or is it something that would require some modification of either these packages themselves or some existing API?
- S. Hirata, M. Head-Gordon, R.J. Bartlett Configuration interaction singles, time-dependent Hartree–Fock, and time-dependent density functional theory for the electronic excited states of extended systems J. Chem. Phys. 111, 10774 (1999); DOI: 10.1063/1.480443