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

ABSTRACT

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.

KEYWORDS:

• Complete basis set limit
• zero-point vibrational correction
• NMR shielding constant
• water
• CCSD(T)

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgments

The authors would like to congratulate Professor Dr. Hans Jørgen Aagaard Jensen on the occasion of his 60th birthday. We wish to express our sincere acknowledgments to the great impact he has had so far on the fields of non-relativistic and relativistic quantum chemistry and the development and maintenance of the DALTON and DIRAC programs. The authors thank the Danish Center for Scientific Computing, the Supercomputing and Networking Center ACK CYFRONET AGH in Krakow (PL-grid on zeus computer) and the Supercomputing and Networking Center in Wroclaw for access to the high-performance computing facilities.

Additional information

Funding

Danish Center for Scientific Computing 2010.04.01.