Origin-independent two-photon circular dichroism calculations in coupled cluster theory.

We present the first origin-independent approach for the treatment of two-photon circular dichro- ism (TPCD) using coupled cluster methods. The approach is assessed concerning its behavior on the choice of basis set and different coupled cluster methods. We also provide a comparison of results from CC2 with those from density functional theory with the CAM-B3LYP functional. Concerning the basis set we note that in most cases an augmented triple zeta basis or a doubly augmented double zeta basis is needed for reasonably converged results. In the comparison of different coupled cluster methods results from CCSD and CC2 have been found to be quite sim- ilar in most cases while CCS results differ remarkably from the results at the higher levels. For most molecules CC2 and DFT compare quite well. We can therefore show that the CAM-B3LYP functional, which has been used in a lot of published studies on TPCD gives reasonable results.