00637nas a2200157 4500008004100000245012300041210006900164260000800233300001200241490000800253100002600261700002700287700001800314700001600332856013100348 2012 eng d00aFock-space multi-reference coupled-cluster response with the effect of triples on dipole moment of ClO and SF radicals0 aFockspace multireference coupledcluster response with the effect cJAN a223-2320 v1241 aRavichandran, Lalitha1 aBhattacharya, Debarati1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/fock-space-multi-reference-coupled-cluster-response-effect-triples-dipole-moment-clo-and-sf01986nas a2200169 4500008004100000022001400041245016600055210006900221260012500290300001100415490000800426520119300434100002701627700001801654700001601672856012801688 2013 eng d a0021-960600aElectronic transition dipole moments and dipole oscillator strengths within fock-space multi-reference coupled cluster framework: an efficient and novel approach0 aElectronic transition dipole moments and dipole oscillator stren aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScMAR a0941080 v1383 a

Within the Fock-space multi-reference coupled cluster framework, we have evaluated the electronic transition dipole moments, which determine absorption intensities. These depend on matrix elements between two different wave functions (e. g., ground state to the excited state). We present two different ways, to calculate these transition moments. In the first method, we construct the ground and excited state wave functions with the normal exponential ansatz of Fock-space coupled cluster method and then calculate the relevant off-diagonal matrix elements. In the second approach, we linearize the exponential form of the wave operator which will generate the left vector, by use of Lagrangian formulation. The right vector is obtained from the exponential ansatz. In order to relate the transition moments to oscillator strengths, excitation energies need to be evaluated. The excitation energies are obtained from the Fock-space multi-reference framework. The transition dipole moments of the ground to a few excited states, together with the oscillator strengths of a few molecules, are presented. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793277]

1 aBhattacharya, Debarati1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/electronic-transition-dipole-moments-and-dipole-oscillator-strengths-within-fock-space-001607nas a2200217 4500008004100000022001400041245012100055210006900176260006700245300001400312490000800326520075300334653003301087653001501120653002401135653004001159100002701199700001801226700001601244856012901260 2014 eng d a0020-760800aElectronic transition dipole moment: a semi-biorthogonal approach within valence universal coupled cluster framework0 aElectronic transition dipole moment a semibiorthogonal approach  a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcSEP a1212-12190 v1143 a

Electronic dipole strengths (square of transition moments) and oscillator strengths are evaluated for various transitions, arising from the ground state to a few valence excited states. Parallel to two other methods of calculating the dipole strength within the Fock-space multireference coupled cluster framework, a new semi-biorthogonal approach is formulated and implemented in this article. This semi-biorthogonal approach can evaluate dipole strengths at a lower computational effort than the biorthogonal approach without compromising on the accuracy. This new method is compared and tested against the previously developed expectation value and biorthogonal approach for various molecular transitions. (C) 2014 Wiley Periodicals, Inc.

10aelectronic transition dipole10aFock-space10aoscillator strength10asemi-biorthogonal expectation value1 aBhattacharya, Debarati1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/electronic-transition-dipole-moment-semi-biorthogonal-approach-within-valence-universal-002044nas a2200229 4500008004100000022001400041245016300055210006900218260009200287300001400379490000800393520108200401653003301483653001501516653002301531653003901554100002701593700002701620700002001647700001601667856013101683 2015 eng d a0026-897600aPerturbative order analysis of the similarity transformed hamiltonian in fock-space coupled cluster theory: difference energy and electric response properties0 aPerturbative order analysis of the similarity transformed hamilt a4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLANDbTAYLOR & FRANCIS LTDcJUL a2046-20600 v1133 a

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.

10aelectric response properties10aFock space10aperturbative order10asimilarity transformed Hamiltonian1 aBhattacharya, Debarati1 aDutta, Achintya, Kumar1 aGupta, Jitendra1 aPal, Sourav uhttps://library.ncl.res.in/content/perturbative-order-analysis-similarity-transformed-hamiltonian-fock-space-coupled-cluster-0