Gaussian basis sets for use in correlated molecular calculations. VIII. Standard and augmented sextuple zeta correlation consistent basis sets for aluminum through argon

Standard and augmented correlation consistent sextuple zeta (cc-pV6Z and au g-cc-pV6Z) basis sets have been determined for the second-row atoms aluminu m through argon. Using these sets, dissociation energies and spectroscopic constants for the ground states of HCl, PN, and P-2 have been calculated us ing several theoretical methods, including Moller-Plesset perturbation theo ry, coupled cluster theory, and multireference configuration interaction th eory (MRCI). The aug-cc-pV6Z and cc-pVbZ sets yield dissociation energies t hat are estimated to be within 0.1-0.2 kcal/mol of the complete basis set l imit for HCl and within 1-1.5 kcal/mol for PN and P-2. The MRCI and CCSD(T) methods are found to give the most Consistently reliable results for the s pectroscopic constants of all three species investigated. Use of the counte rpoise correction improves the convergence behavior of the spectroscopic co nstants with increasing n for both the cc-pVnZ and aug-cc-pVnZ sets and sho uld allow more accurate estimates of the complete basis set Limit to be pre dicted. (C) 2000 John Wiley & Sons, Inc.