On the convergence of zero-point vibrational corrections to nuclear shieldings and shielding anisotropies towards the complete basis set limit in water

• Published in: Molecular physics Vol. 115; no. 1-2; pp. 144 - 160
• Main Authors: Faber, Rasmus, Buczek, Aneta, Kupka, Teobald, Sauer, Stephan P. A.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 17.01.2017; Taylor & Francis Ltd
• Subjects: Anisotropy; Approximation; CCSD(T); Clusters; Complete basis set limit; Convergence; Extrapolation; Magnetic shielding; NMR shielding constant; Permissible error; Perturbation theory; water; zero-point vibrational correction
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2016.1210831

The method and basis set dependence of zero-point vibrational corrections (ZPVCs) to nuclear magnetic resonance shielding constants and anisotropies has been investigated using water as a test system. A systematic comparison has been made using the Hartree-Fock, second-order Møller-Plesset perturbation theory (MP2), coupled cluster singles and doubles (CCSD), coupled cluster singles and doubles with perturbative triples corrections (CCSD(T)) and Kohn-Sham density functional theory with the B3LYP exchange-correlation functional methods in combination with the second-order vibrational perturbation theory (VPT2) approach for the vibrational corrections. As basis sets, the correlation consistent basis sets cc-pVXZ, aug-cc-pVXZ, cc-pCVXZ and aug-cc-pCVXZ with X = D, T, Q, 5, 6 and the polarisation consistent basis sets aug-pc-n and aug-pcS-n with n = 1, 2, 3, 4 were employed. Our results show that basis set convergence of the vibrational corrections is not monotonic and that very large basis sets are needed before a reasonable extrapolation to the basis set limit can be performed. Furthermore, our results suggest that coupled cluster methods and a decent basis set are required before the error of the electronic structure approach is lower than the inherent error of the VPT2 approximation.