Title :

Perturbative Approximations to Spin Flip Coupled Cluster Singles Doubles - Application to Bond Breaking Problem


Spin flip equation of motion coupled cluster (EOM-SF-CC) can correctly treat situations involving electronic degeneracies or near degeneracies, e.g, bond breaking, di- and tri-radicals etc. However, for large systems EOM-SF-CC (even in single and double excitations) is
computationally prohibitively expensive. Therefore, earlier approximations to EOM-SF-CC methods such as spin flip configuration interaction singles with perturbative doubles (SF-CIS(D)) has been proposed. In this talk, I will present a new perturbative approximation to EOM-SF-CC, which has been found to be more accurate than the earlier SF-CIS(D). The capabilities, advantages and timings of the new approach will be demonstrated through bond breaking problems, oxirane ring opening and cyclo-butadiene automerization reaction.


1.      A. K. Dutta, S. Pal And D. Ghosh, Perturbative approximations to single and double spin flip equation of motion coupled cluster singles doubles methods, J. Chem. Phys., 139, 124116  (2013).

2.      D. Ghosh, Perturbative approximation to hybrid equation of motion coupled cluster / effective fragment potential method, J. Chem. Phys., 140, 094101 (2014).