In this Letter we extend the XZP basis sets (X = D and T) developed by Jorge et al. for Li-Ar atoms with the tight functions and optimize these functions using the criterion of maximizing the core correlation energy (CCE) developed by Woon and Dunning. The basis sets generated with this method were designated as CXZP. Our results showed CCE of the CXZP sets compared to the XZP sets were between 153 and 240 millihartrees (for Na-Ar). Applications in calculations of NMR indirect spin-spin coupling constants at the B3LYP and SOPPA levels were performed. (C) 2012 Elsevier B.V. All rights reserved.