q-AQUA

The a-AQUA dataset was generated to address the need for a training set for a water PES that includes 2-body, 3-body and 4-body interactions calculated at the CCSD(T) level of theory. Structures were selected from the existing HBB2-pol and MB-pol datasets. For each water dimer structure, CCSD(T)/aug-cc-pVTZ calculations were performed with an additional 3s3p2d1f basis set; exponents equal to (0.9, 0.3, 0.1) for sp, (0.6, 0.2) for d, and 0.3 for f. This additional basis is placed at the center of mass (COM) of each dimer configuration. The basis set superposition error (BSSE) correction was determined with the counterpoise scheme. CCSD(T)/aug-cc-pVQZ calculations were then performed with the same additional basis set and BSSE correction. Final CCSD(T)/CBS energies were obtained by extrapolation over the CCSD(T)/aug-cc-pVTZ and CCSD(T)/aug-cc-pVQZ 2-b energies. All ab initio calculations were performed using Molpro package.Trimer structures were calculated at CCSD(T)-F12a/aug-cc-pVTZ with BSSE correction. Four-body structure calculations were performed at CCSD(T)-F12 level.