@conference { ISI:000252146200027, title = {Constrained variational response to fock-space multi-reference coupled-cluster theory: formulation for excited-state electronic structure calculations and some pilot applications}, booktitle = {Computational Methods in Science and Engineering Vol 1: Theory and Computation: Old Problems and New Challenges}, series = {AIP CONFERENCE PROCEEDINGS}, volume = {963}, year = {2007}, note = {International Conference on Computational Methods in Science and Engineering, Corfu, GREECE, SEP 25-30, 2007}, month = {SEP}, pages = {337-344}, publisher = {European Soc Computat Methods Sci \& Engn; Minist Natl Educ \& Religious Affairs; E4 Comp Engn}, organization = {European Soc Computat Methods Sci \& Engn; Minist Natl Educ \& Religious Affairs; E4 Comp Engn}, address = {2 Huntington Quadrangle, Ste 1no1, Melville, NY 11747-4501 USA}, abstract = {

Fock-space (FS) multi-reference (MR) coupled-cluster (CC) method has emerged as compact tool to account for electronic structure of open-shell systems and molecules in low-lying excited states. Development of linear response (LR) has been one of the challenging problems in FSMRCC due to multiple-root nature of effective Hamiltonian. The recently developed constrained variational approach (CVA) has opened up a promising tool for efficient evaluation of analytic response properties. In this article, we present formulation of the method for excited state calculations. We discuss the decoupling of equations as a result of spin-adaptation and present some preliminary results for analytical dipole moments and polarizabilities of some molecules in low-lying triplet excited states.

}, keywords = {CVA, Dipole moment, excited states, FSMRCC, polarizability}, isbn = {978-0-7354-0477-9}, issn = {0094-243X}, author = {Manohar, Prashant Uday and Pal, Sourav}, editor = {Maroulis, G and Simos, TE} } @conference { ISI:000354845400032, title = {Partial triples excitation to the fock space multi-reference singles and doubles: dipole moment of doublet radicals}, booktitle = {Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2010 (ICCMSE-2010)}, series = {AIP Conference Proceedings}, volume = {1642}, year = {2015}, note = {International Conference of Computational Methods in Sciences and Engineering (ICCMSE), Kos, GREECE, OCT 03-08, 2010}, month = {FEB}, pages = {223-226}, publisher = {European Soc Computat Methods Sci, Engn \& Technol}, organization = {European Soc Computat Methods Sci, Engn \& Technol}, address = {2 Huntington Quadrangle, STE 1NO1, Melville, NY 11747-4501 USA}, abstract = {

We present the partial triples effect on the dipole moment of doublet radicals in Lagrangian formulation of Fockspace multi-reference coupled cluster response method(A FSMRCC). This specific scheme uses non-iterative triples, in addition to singles and doubles excitations(A FSMRCCSD(T*)), which accounts for the effects appearing at least at the third order in dipole moment. This method is applied to the ground states of small radicals.

}, keywords = {Dipole moment, Multi-reference, Triples}, isbn = {978-0-7354-1282-8}, issn = {0094-243X}, doi = {10.1063/1.4906657}, author = {Ravichandran, Lalitha and Vaval, Nayana and Pal, Sourav}, editor = {Simos, TE and Maroulis, G} } @conference { ISI:000354845400033, title = {Study of molecular vibration by coupled cluster method: bosonic approach}, booktitle = {Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2010 (ICCMSE-2010)}, series = {AIP Conference Proceedings}, volume = {1642}, year = {2015}, note = {International Conference of Computational Methods in Sciences and Engineering (ICCMSE), Kos, GREECE, OCT 03-08, 2010}, month = {FEB}, pages = {227-230}, publisher = {European Soc Computat Methods Sci, Engn \& Technol}, organization = {European Soc Computat Methods Sci, Engn \& Technol}, address = {2 Huntington Quadrangle, STE 1NO1, Melville, NY 11747-4501 USA}, abstract = {

The vibrational coupled cluster method in bosonic representation is formulated to describe the molecular anharmonic vibrational spectra. The vibrational coupled cluster formalism is based on Watson Hamiltonian in normal coordinates. The vibrational excited states are described using coupled cluster linear response theory (CCLRT). The quality of the coupled cluster wave function is analyzed. Specifically, the mean displacement values of the normal coordinates and expectation values of the square of the normal coordinates of different vibrational states are calculated. A good agreement between the converged full CI results and coupled cluster results is found for the lower lying vibrational states.

}, keywords = {CCLRT, Expectation values, Watson Hamiltonian}, isbn = {978-0-7354-1282-8}, issn = {0094-243X}, doi = {10.1063/1.4906658}, author = {Banik, Subrata and Pal, Sourav and Prasad, M. Durga}, editor = {Simos, TE and Maroulis, G} }