01512nas a2200169 4500008004100000022001400041245014100055210006900196260012500265300001100390490000800401520076400409100001401173700001401187700001101201856013001212 2005 eng d a0021-960600aAnalytically continued Fock space multireference coupled-cluster theory: application to the (2)Pi(g) shape resonance in e-N-2 scattering0 aAnalytically continued Fock space multireference coupledcluster  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScJUN a2343200 v1223 a

The technique of Fock space multireference coupled-cluster (FSMRCC) is applied for the first time to the correlated calculation of the energy and width of a shape resonance in an electron-molecule collision. The procedure is based upon combining a complex absorbing potential with FSMRCC theory. Accurate resonance parameters are obtained by solving a small non-Hermitian eigenvalue problem. The potential-energy curve of the (2)Pi(g) state of N-2(-) is calculated using the FSMRCC and multireference configuration-interaction (MRCI) level of theories. Comparison with the single-determinant Hartree-Fock theory indicates that correlation effects are important in determining the behavior of the resonance state. (C) 2005 American Institute of Physics.

1 aSajeev, Y1 aSantra, R1 aPal, S uhttps://library.ncl.res.in/content/analytically-continued-fock-space-multireference-coupled-cluster-theory-application-2pig-101939nas a2200169 4500008004100000022001400041245009200055210006900147260012500216300001100341490000800352520124500360100001401605700001401619700001101633856012501644 2005 eng d a0021-960600aCorrelated complex independent particle potential for calculating electronic resonances0 aCorrelated complex independent particle potential for calculatin aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScNOV a2041100 v1233 a

We have formulated and applied an analytic continuation method for the recently formulated correlated independent particle potential [A. Beste and R. J. Bartlett J. Chem. Phys. 120, 8395 (2004)] derived from Fock space multireference coupled cluster theory. The technique developed is an advanced ab initio tool for calculating the properties of resonances in the low-energy electron-molecule collision problem. The proposed method quantitatively describes elastic electron-molecule scattering below the first electronically inelastic threshold. A complex absorbing potential is utilized to define the analytic continuation for the potential. A separate treatment of electron correlation and relaxation effects for the projectile-target system and the analytic continuation using the complex absorbing potential is possible, when an approximated form of the correlated complex independent particle potential is used. The method, which is referred to as complex absorbing potential-based correlated independent particle (CAP-CIP), is tested by application to the well-known (2)Pi(g) shape resonance of e-N-2 and the B-2(2g) shape resonance of e-C2H4 (ethylene) with highly satisfactory results. (c) 2005 American Institute of Physics.

1 aSajeev, Y1 aSantra, R1 aPal, S uhttps://library.ncl.res.in/content/correlated-complex-independent-particle-potential-calculating-electronic-resonances-101221nas a2200181 4500008004100000022001400041245012800055210006900183260009200252300001400344490000800358520043700366653002600803653005300829100001400882700001100896856013200907 2005 eng d a0026-897600aGeneral formalism of the Fock space multireference coupled cluster method for investigating molecular electronic resonances0 aGeneral formalism of the Fock space multireference coupled clust a4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLANDbTAYLOR & FRANCIS LTDcAUG a2267-22750 v1033 a

Electron correlation and relaxation effects play a substantial role in the formation and decay of resonance states. In this paper we formulate a complex absorbing potential combined with the Fock space multireference coupled cluster method for the correlated calculations of resonance energy and width. This can describe the dynamic and non-dynamic electron correlation efficiently in the ionized or electron attached states.

10aelectronic resonances10aFock space multireference coupled cluster method1 aSajeev, Y1 aPal, S uhttps://library.ncl.res.in/content/general-formalism-fock-space-multireference-coupled-cluster-method-investigating-molecular-001185nas a2200181 4500008004100000022001400041245013200055210006900187260007100256300001600327490000800343520047100351100001300822700001700835700001400852700001100866856012600877 2005 eng d a1520-610600aOptimization of nonlinear optical properties by substituent position, geometry and symmetry of the molecule: an ab initio study0 aOptimization of nonlinear optical properties by substituent posi a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUL a14093-141010 v1093 a

Static polarizability and first- and second-order hyperpolarizability tensors are computed at the correlated level for a series of para-nitroaniline derivatives. The importance of including electron correlation effects in the determination of equilibrium structure and the molecular properties is investigated. A qualitative description of the substitution effects, planarity, and symmetric effect of the molecule on the molecular susceptibility is discussed.

1 aDavis, D1 aSreekumar, K1 aSajeev, Y1 aPal, S uhttps://library.ncl.res.in/content/optimization-nonlinear-optical-properties-substituent-position-geometry-and-symmetry-0