Basis Set Convergence of Indirect Spin−Spin Coupling Constants in the Kohn−Sham Limit for Several Small Molecules

The performance of more than 40 density functionals in predicting indirect spin−spin coupling constants (SSCCs) in the Kohn− Sham basis set limit was tested. For comparison, similar calculations were performed using the RHF, SOPPA, SOPPA(CC2), and SOPPA(CCSD) methods, and the results were estimated toward the complete basis set (CBS) limit. The SSCCs of nine small molecules (N2, CO, CO2 ,N H3 ,C H4, C2H2 ,C 2H4 ,C 2H6, and C6H6) were calculated using the dedicated Jensen pcJ-n polarization-consistent basis sets and used for the CBS limit estimations within the Kohn−Sham limit. These CBS results were compared with calculations using the aug-cc-pVTZ-J basis set. Among the 41 studied DFT methods, the tHCTHhyb, HSEh1PBE, HSE2PBE, wB97XD, wB97, and wB97X functionals reproduced accurately the experimental 1 J(XH) SSCCs and 3 J(HH60) and 2 J(HHgem) in ethane. Similarly, the functionals HSEh1PBE, HSE2PBE, wB97XD, wB97, and wB97X predicted accurately 1 J(CC), and B98, B97-1, B97-2, PBE1PBE, B1LYP, and O3LYP provided accurate 1 J(CO) results in the CO molecule. A very good performance for the calculation of the SSCCs based on the use of the relatively small basis set aug-cc-pVTZ-J was observed.