@article { ISI:000323509900012,
	title = {Lagrange multiplier approach for excited state properties through intermediate hamiltonian formulation of fock space multireference coupled-cluster theory},
	journal = {Journal of Chemical Physics},
	volume = {139},
	number = {7},
	year = {2013},
	month = {AUG},
	pages = {074108},
	publisher = {AMER INST PHYSICS},
	address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA},
	abstract = {<p>In this paper, we present a formulation based on Lagrange multiplier approach for efficient evaluation of excited state energy derivatives in Fock space coupled cluster theory within the intermediate Hamiltonian framework. The formulation is applied to derive the explicit generic expressions up to second order energy derivatives for [1, 1] sector of Fock space with singles and doubles approximation. Its advantage, efficiency, and interconnection in comparison to the Lagrange multiplier approach in traditional formulation of Fock space, which is built on the concept of Bloch equation based effective Hamiltonian, has been discussed. Computational strategy for their implementation has also been discussed in some detail. (C) 2013 AIP Publishing LLC.</p>},
	issn = {0021-9606},
	doi = {10.1063/1.4817943},
	author = {Gupta, Jitendra and Vaval, Nayana and Pal, Sourav}
}
@article {42627,
	title = {Lifetime of inner-shell hole states of Ar (2p) and Kr (3d) using equation-of-motion coupled cluster method},
	journal = {Journal of Chemical Physics},
	volume = {143},
	year = {2015},
	month = {JUL},
	pages = {Article No. 024305},
	doi = {10.1063/1.4926396},
	author = {Ghosh, Aryya and Pal, Sourav and Vaval, Nayana}
}
@article {44617,
	title = {Lower scaling approximation to EOM-CCSD: a critical assessment of the ionization problem},
	journal = {International Journal of Quantum Chemistry},
	volume = {118},
	year = {2018},
	month = {JUL},
	pages = {e25594},
	abstract = {<p>In this article, we investigate the performance of different approximate variants of the EOM-CCSD method for calculation of ionization potential (IP), as compared to EOM-CCSDT reference values. None of the lower scaling approximations to the EOM-CCSD method give a consistent performance for valence, inner valence, and core ionization, favoring one, or the other depending on the nature of the approximation used. The parent EOMIP-CCSD method gives superior performance for valence IP but can show large errors for inner valence and core ionization. The problem is particularly severe for core-ionization, where even the EOMIP-CCSDT method cannot provide quantitative accuracy.</p>},
	keywords = {EOM-CCSD, Ionization potential, lower scaling},
	issn = {0020-7608},
	doi = {10.1002/qua.25594},
	author = {Dutta, Achintya Kumar and Vaval, Nayana and Pal, Sourav}
}
