@article { ISI:000325392000050,
	title = {Perturbative approximations to single and double spin flip equation of motion coupled cluster singles doubles methods},
	journal = {Journal of Chemical Physics},
	volume = {139},
	number = {12},
	year = {2013},
	month = {SEP},
	pages = {124116},
	publisher = {AMER INST PHYSICS},
	address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA},
	abstract = {<p>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)) have been proposed. In this work, we present a new perturbative approximation to EOM-SF-CC, which has been found to be more accurate than SF-CIS(D). The capabilities, advantages, and timings of the new approach have been demonstrated considering the singlet-triplet gaps in di- and triradicals as well as bond breaking examples. The method is extended to double spin flip EOM-CC and its capabilities have been tested. (C) 2013 AIP Publishing LLC.</p>},
	issn = {0021-9606},
	doi = {10.1063/1.4821936},
	author = {Dutta, Achintya Kumar and Pal, Sourav and Ghosh, Debashree}
}
