Frequency dependent equation-of-motion coupled cluster hyperpolarizabilities: Resolution of the discrepancy between theory and experiment for HF?

We formulate and apply the EOM-CC method to determine, recursively, any order and any process frequency dependent hyperpolarizability. Combining the theory with systematically chosen n-aug-cc-pVXZ bases, we attempt to converge to the basis set limit. Our best “relaxed” result is −9.8±0.5 a.u. for βSHG compared to an experimental value of −11.0±1 a.u. and 720±40 a.u. for γdc-SHG compared to 840±120 a.u. If orbital relaxation could be neglected, the results are −10.2±0.5 a.u. and 730±40 a.u., falling within the error bars.