01966nas a2200241 4500008004100000020001800041022001400059245007800073210006900151260009500220300001200315490000600327520112400333653003001457653002501487653001901512653002201531100001601553700001801569700001601587700001301603856010801616 2005 eng d a90-6764-442-0 a1573-419600aDensity functional response approach for electric properties of molecules0 aDensity functional response approach for electric properties of  aCorinth, GreecebVsp BV-C/o Brill Acad Publ, Po Box 9000, 2300 Pa Leiden, NetherlandscOCT a142-1510 v33 a

We review in this paper an implementation of the response approach to the Kohn-Sham (KS) density functional theory (DFT) for obtaining the linear and non-linear electric response properties of molecules using Gaussian type orbital basis centered on atoms. We have made a formulation in which the response of the electron density through the solution of the coupled perturbed Kohn-Sham (CPKS) equations has to be obtained only once, instead of iteratively as in the case of completely analytic procedure. Our method is based on a numerical finite-field solution of derivative KS operator, followed by analytic solution of CPKS equation. Further, using the response of the electron density, the dipole moment, polarizability and first-hyperpolarizability of the molecules are evaluated. The method is particularly useful for large systems. We tested our method using HF, BH, H2O and CO as test molecules, for which, high quality ab initio results are available. Further, our study of possible incorporation of non-dynamical electron correlation by studying BH and HF at several internuclear distances is discussed.

10aDensity functional theory10amolecular properties10apolarizability10aResponse approach1 aPal, Sourav1 aSophy, K., B.1 aMaroulis, G1 aSimos, T uhttps://library.ncl.res.in/content/density-functional-response-approach-electric-properties-molecules-001838nas a2200253 4500008004100000020002200041022001400063245018300077210006900260260016600329300001200495490000800507520079600515653000801311653001801319653001901337653001101356653001901367100002801386700001601414700001601430700001401446856012401460 2007 eng d a978-0-7354-0477-9 a0094-243X00aConstrained variational response to fock-space multi-reference coupled-cluster theory: formulation for excited-state electronic structure calculations and some pilot applications0 aConstrained variational response to fockspace multireference cou a2 Huntington Quadrangle, Ste 1no1, Melville, NY 11747-4501 USAbEuropean Soc Computat Methods Sci & Engn; Minist Natl Educ & Religious Affairs; E4 Comp EngncSEP a337-3440 v9633 a

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.

10aCVA10aDipole moment10aexcited states10aFSMRCC10apolarizability1 aManohar, Prashant, Uday1 aPal, Sourav1 aMaroulis, G1 aSimos, TE uhttps://library.ncl.res.in/content/constrained-variational-response-fock-space-multi-reference-coupled-cluster-theory-001372nas a2200241 4500008004100000020002200041022001400063245012000077210006900197260012300266300001200389490000900401520045100410653001800861653002000879653001200899100002600911700001800937700001600955700001400971700001600985856012901001 2015 eng d a978-0-7354-1282-8 a0094-243X00aPartial triples excitation to the fock space multi-reference singles and doubles: dipole moment of doublet radicals0 aPartial triples excitation to the fock space multireference sing a2 Huntington Quadrangle, STE 1NO1, Melville, NY 11747-4501 USAbEuropean Soc Computat Methods Sci, Engn & TechnolcFEB a223-2260 v16423 a

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.

10aDipole moment10aMulti-reference10aTriples1 aRavichandran, Lalitha1 aVaval, Nayana1 aPal, Sourav1 aSimos, TE1 aMaroulis, G uhttps://library.ncl.res.in/content/partial-triples-excitation-fock-space-multi-reference-singles-and-doubles-dipole-moment-001602nas a2200241 4500008004100000020002200041022001400063245007700077210006900154260012300223300001200346490000900358520074700367653001001114653002301124653002301147100001901170700001601189700001801205700001401223700001601237856010701253 2015 eng d a978-0-7354-1282-8 a0094-243X00aStudy of molecular vibration by coupled cluster method: bosonic approach0 aStudy of molecular vibration by coupled cluster method bosonic a a2 Huntington Quadrangle, STE 1NO1, Melville, NY 11747-4501 USAbEuropean Soc Computat Methods Sci, Engn & TechnolcFEB a227-2300 v16423 a

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.

10aCCLRT10aExpectation values10aWatson Hamiltonian1 aBanik, Subrata1 aPal, Sourav1 aPrasad, Durga1 aSimos, TE1 aMaroulis, G uhttps://library.ncl.res.in/content/study-molecular-vibration-coupled-cluster-method-bosonic-approach-0