A Local Pair Natural Orbital-Based Multireference Mukherjee’s Coupled Cluster Method

• Published in: Journal of Chemical Theory and Computation
• Main Authors: Demel, O., Pittner, J., Neese, F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: Orca
• Online Access: http://hdl.handle.net/21.11116/0000-0007-8964-E

This paper reports the development of a local variant of Mukherjee’s state-specific multireference coupled cluster method based on the pair natural orbital approach (LPNO-MkCC). The current implementation is restricted to single and double excitations. The performance of the LPNO-MkCCSD method was tested on calculations of naphthyne isomers, tetramethyleneethane, and β-carotene molecules. The results show that 99.7–99.8% of correlation energy was recovered with respect to the MkCC method based on canonical orbitals. Moreover, the errors of relative energies between different isomers or along a potential energy curve (with respect to the canonical method) are below 0.4 kcal/mol, safely within the chemical accuracy. The computational efficiency of our implementation of LPNO-MkCCSD in the ORCA program allows calculation of the β-carotene molecule (96 atoms and 1984 basis functions) on a single CPU core.