Towards large-scale calculations with State-Specific Multireference Coupled Cluster methods: Studies on dodecane, naphthynes, and polycarbenes

Multireference Coupled Cluster (MRCC) methods are essential for accurate descriptions of molecular systems with degenerate states. However, their use has been hampered by their high computational cost, which can be alleviated with scalable MRCC codes. Exploiting large computational resources our recent parallelization work has demonstrated MRCC on chemically relevant molecules within practical per core resource constraints. We report on parallel implementations of Mukherjee's MRCC (MR MkCCSD) and Brillouin-Wigner MRCC (MR BWCC) models. Especially abstracting a methyl-group from dodecane, and singlet-high-spin splittings in naphthyne isomers and polycarbenes demonstrate systems with significant multireference character and size that currently can be handled. (C) 2012 Elsevier B. V. All rights reserved.