@article { ISI:000267086900013, title = {Magnetizability of doublet radicals using fock space multi-reference coupled cluster method}, journal = {International Journal of Quantum Chemistry}, volume = {109}, number = {10, SI}, year = {2009}, month = {AUG}, pages = {2191-2198}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

In this article, we report the first implementation of the recently developed Fock space multi reference Coupled cluster (FSMRCC) response approach for magnetizabilities. The FSM-RCC treats dynamic and static correlation in a very extensive manner. We report pilot application of the diarnagnetizability of NO, NO2, OH, and BH2 radicals. We also report preliminary applications of the paramagnetic magnetizability of the NO radical. Standard atom-centered Gaussian basis functions have been used, and this allowed US to Study the gauge dependence of the magnetizabilities. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 2191-2198, 2009

}, keywords = {Fock space, magnetizability, multireference}, issn = {0020-7608}, doi = {10.1002/qua.22093}, author = {Ravichandran, Lalitha and Vaval, Nayana and Pal, Sourav} } @article { ISI:000284635100022, title = {Fock space multi-reference coupled-cluster method for energies and energy derivatives}, journal = {Molecular Physics}, volume = {108}, number = {21-23, SI}, year = {2010}, month = {OCT}, pages = {PII 927961714}, publisher = {TAYLOR \& FRANCIS LTD}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

In this article, the development of Fock space multi-reference coupled-cluster method is reviewed. Molecular applications of the method for excitation and ionisation energies which took place at Quantum Theory Project have been discussed. Later developments of the method for energy derivatives have been presented along with pilot applications of molecular properties of radicals and excited states.

}, keywords = {coupled-cluster, difference energies, energy derivatives, Fock space, Multi-reference}, issn = {0026-8976}, doi = {10.1080/00268976.2010.522205}, author = {Pal, Sourav} } @article { ISI:000357933400054, title = {Perturbative order analysis of the similarity transformed hamiltonian in fock-space coupled cluster theory: difference energy and electric response properties}, journal = {Molecular Physics}, volume = {113}, number = {13-14, SI}, year = {2015}, month = {JUL}, pages = {2046-2060}, publisher = {TAYLOR \& FRANCIS LTD}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

A perturbative analysis of the ground-state similarity transformed Hamiltonian and its effect on the various Fock-space coupled cluster (FSCC) sectors is presented through calculation of ionisation potential, electron affinity, excitation energies and response properties. Various truncation schemes of the effective Hamiltonian are presented with explicit form of the defining equations. Based on such a truncation, the approximate methods are labelled as FSCC(n), where n represents the correlation energy of the ionised, electron attached or excited states corrected at least up to nth order within coupled cluster singles and doubles scheme (CCSD). A lower scaling CC2 type of approach (abbreviated as FS-CC2) is compared against the group of FSCC(n) methods for energies. Electric response properties have been compared and contrasted for the two lower scaling methods: FSCC(2) and FS-CC2. The various truncated methods are tested for a number of small molecules. The results obtained from a range of truncated methods are compared against full FSCCSD calculations.

}, keywords = {electric response properties, Fock space, perturbative order, similarity transformed Hamiltonian}, issn = {0026-8976}, doi = {10.1080/00268976.2015.1059509}, author = {Bhattacharya, Debarati and Dutta, Achintya Kumar and Gupta, Jitendra and Pal, Sourav} }