02149nas a2200229 4500008004100000022001400041245011300055210006900168260005700237300000900294490000800303520130600311653000801617653003301625653003701658653002301695653001301718100002301731700002201754700001601776856012701792 2012 eng d a1432-881X00aBehaviour of density functional theory for electric response properties at distorted geometries of molecules0 aBehaviour of density functional theory for electric response pro a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcFEB a10940 v1313 a

The role of exchange-correlation is well known for accurate calculations of electric response properties. The exchange-correlation functional in density functional theory (DFT) has been well studied for ground state equilibrium geometry. However, the behaviour of these functional in stretched geometries, where static correlation play an important role, has not been studied systematically, particularly for response electric properties. Thus, we present here the rigorous calculation of electric response properties at distorted geometries of the molecules. We have considered dipole polarizability and dipole-quadrupole polarizability for description of role of static and dynamic correlation for electric response properties. The calculations are performed with our new approach, noniterative approximation to coupled-perturbed Kohn-Sham method. These DFT results are compared with higher level ab initio such as coupled perturbed singles and doubles and fully correlated full CI. We have studied single, double and triple-bonded systems at different inter-nuclear separation. We report here the dipole polarizability and dipole-quadrupole polarizability of HF, BH, H2CO, CO and NO+. We also present the effect of basis and functional on polarizability and dipole-quadrupole polarizability.

10aDFT10aDipole-dipole polarizability10aDipole-quadrupole polarizability10aDistorted geometry10aNIA-CPKS1 aShedge, Sapana, V.1 aJoshi, Sayali, P.1 aPal, Sourav uhttps://library.ncl.res.in/content/behaviour-density-functional-theory-electric-response-properties-distorted-geometries-001711nas a2200217 4500008004100000022001400041245007900055210006900134260007300203300001000276490000800286520092600294653002901220653003001249653002201279100002201301700002701323700001601350700001801366856010901384 2012 eng d a0301-010400aExtended coupled cluster for Raman and infrared spectra of small molecules0 aExtended coupled cluster for Raman and infrared spectra of small aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL a25-320 v4033 a

In this paper we study the harmonic vibrational frequencies, infrared (IR) intensities, Raman intensities and depolarization ratio using extended coupled cluster method. Raman and IR intensities are mixed derivatives of energy with respect to the electric field and geometric perturbation whereas vibrational frequencies are derivatives of energy with respect to geometry. We use semi-numerical approach to obtain these derivatives. We have studied the effect of electron correlation and basis set for the above properties. We compare our results with non-variational coupled cluster and experimental values, wherever available. We have studied HF, BH, CH+, CO and H2CO molecules in different basis sets. For HF molecule, benchmarking is done with full CI values and basis set convergence is studied for this molecule. Effect of triples is studied for all the molecules. (C) 2012 Elsevier B.V. All rights reserved.

10aExtended coupled cluster10aIR and Raman spectroscopy10aMixed derivatives1 aJoshi, Sayali, P.1 aDutta, Achintya, Kumar1 aPal, Sourav1 aVaval, Nayana uhttps://library.ncl.res.in/content/extended-coupled-cluster-raman-and-infrared-spectra-small-molecules-001299nas a2200157 4500008004100000022001400041245006000055210006000115260007300175300001200248490000800260520073600268100002201004700001801026856009701044 2013 eng d a0009-261400aMultipole moments using extended coupled cluster method0 aMultipole moments using extended coupled cluster method aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAY a170-1750 v5683 a

Using analytic extended coupled cluster (ECC) response approach quadrupole moments, dipole-quadrupole polarizabilities and dipole polarizabilities are studied. In the current implementation of the functional we have included all the double linked terms within (CCSD) approximation. These terms will be important for the accurate description of properties at the stretched geometries. We report the properties for carbon monoxide and hydrogen fluoride molecules, as a function of bond distance and compare our results for carbon monoxide with the full Cl results. We have also reported the properties of methane, tetrafluoromethane, acetylene, difluoroacetylene, water and ammonia. (C) 2013 Elsevier B.V. All rights reserved.

1 aJoshi, Sayali, P.1 aVaval, Nayana uhttps://library.ncl.res.in/content/multipole-moments-using-extended-coupled-cluster-method-001209nas a2200157 4500008004100000022001400041245008700055210006900142260007300211300001200284490000800296520059000304100002200894700001800916856011700934 2014 eng d a0009-261400aExtended coupled cluster method for potential energy surface: a decoupled approach0 aExtended coupled cluster method for potential energy surface a d aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcSEP a209-2130 v6123 a

Extended coupled cluster (ECC) method has been implemented extensively for the calculation of molecular properties. In this Letter we report the potential energy surface (PES) study using coupled and a decoupled approximation of ECC. HF, N-2 and C-2 are studied as test systems. N-2 and C-2 being doubly and triply bonded, are considered to be interesting systems for PES study. We compare our results with full CI (FCI) results wherever available. Decoupled approach within ECC framework shows good convergence for all the molecules. (C) 2014 Elsevier B.V. All rights reserved.

1 aJoshi, Sayali, P.1 aVaval, Nayana uhttps://library.ncl.res.in/content/extended-coupled-cluster-method-potential-energy-surface-decoupled-approach-0