Highly accurate incremental CCSD(T) calculations on aqua- and amine-complexes

Abstract

In this work, the accuracy of the second-order incremental expansion using the domain-specific basis set approach is tested for 20 cationic metal-aqua and 25 cationic metal-amine complexes. The accuracy of the approach is analysed by the statistical measures range, arithmetic mean, mean absolute deviation, root mean square deviation and standard deviation. Using these measures we find that the error due to the local approximations decreases with increasing basis set. Next we construct a local virtual space using projected atomic orbitals (PAOs). The accuracy of the incremental series in combination with a distance-based truncation of the PAO space is analysed and compared to the convergence of the incremental series within the domain-specific basis set approach. Furthermore, we establish the recently proposed incremental CCSD(T)|MP2 method as a benchmark method to obtain highly accurate CCSD(T) energies. In combination with a basis set of quintuple-ζ quality we establish benchmarks for the binding energies of the investigated complexes. Finally, we use the inc-CCSD(T)|MP2/aV5Z’ binding energies of 45 complexes and 34 dissociation reactions to compute the accuracy of several state of the art density functional theory (DFT) functionals like BP86, B3LYP, CAM-B3LYP, M06, PBE0 and TPSSh. With our implementation of the incremental scheme it was possible to compute the inc-CCSD(T)|MP2/aV5Z’ energy for Al(H₂O)³⁺ ₂₅ (6106 AOs).

Keywords:

• incremental scheme
• electron correlation methods
• plesset perturbation-theory
• zeta basis sets
• ab initio

Acknowledgements

The authors thank the Fonds der Chemischen Industrie for financial support, Kirk A. Peterson for providing the quintuple-ζ basis sets for Be and Mg and the referees for their helpful and constructive comments.

Supporting Information Available

The supplementary material contains the RI-BP86/def-TZVP optimised structures (xyz-format) and the total energies.