@conference { ISI:000238284200016, title = {Density functional response approach for electric properties of molecules}, booktitle = {International Conference on Computational Methods in Sciences and Engineering (ICCMSE 2005)}, series = {LECTURE SERIES ON COMPUTER AND COMPUTATIONAL SCIENCES}, volume = {3}, year = {2005}, note = {International Conference on Computational Methods in Sciences and Engineering (ICCMSE 2005), Corinth, GREECE, OCT 21-26, 2005}, month = {OCT}, pages = {142-151}, publisher = {Vsp BV-C/o Brill Acad Publ, Po Box 9000, 2300 Pa Leiden, Netherlands}, organization = {Vsp BV-C/o Brill Acad Publ, Po Box 9000, 2300 Pa Leiden, Netherlands}, address = {Corinth, Greece}, abstract = {

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.

}, keywords = {Density functional theory, molecular properties, polarizability, Response approach}, isbn = {90-6764-442-0}, issn = {1573-4196}, author = {Pal, Sourav and Sophy, K. B.}, editor = {Maroulis, G and Simos, T} } @conference { ISI:000252146200027, title = {Constrained variational response to fock-space multi-reference coupled-cluster theory: formulation for excited-state electronic structure calculations and some pilot applications}, booktitle = {Computational Methods in Science and Engineering Vol 1: Theory and Computation: Old Problems and New Challenges}, series = {AIP CONFERENCE PROCEEDINGS}, volume = {963}, year = {2007}, note = {International Conference on Computational Methods in Science and Engineering, Corfu, GREECE, SEP 25-30, 2007}, month = {SEP}, pages = {337-344}, publisher = {European Soc Computat Methods Sci \& Engn; Minist Natl Educ \& Religious Affairs; E4 Comp Engn}, organization = {European Soc Computat Methods Sci \& Engn; Minist Natl Educ \& Religious Affairs; E4 Comp Engn}, address = {2 Huntington Quadrangle, Ste 1no1, Melville, NY 11747-4501 USA}, abstract = {

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.

}, keywords = {CVA, Dipole moment, excited states, FSMRCC, polarizability}, isbn = {978-0-7354-0477-9}, issn = {0094-243X}, author = {Manohar, Prashant Uday and Pal, Sourav}, editor = {Maroulis, G and Simos, TE} } @article { ISI:000287163800020, title = {Ab initio calculations of the geometry and polarizabilities of bisphenyls having aliphatic substituents}, journal = {International Journal of Quantum Chemistry}, volume = {111}, number = {5}, year = {2011}, month = {APR}, pages = {1092-1100}, publisher = {WILEY-BLACKWELL}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

Ab initio geometry optimization and polarizability calculations of a series of bisphenyls, which are the model compounds of chemically different polycarbonates using HF/6-31G and 6-31G** basis sets are presented. Calculated absolute value of the conformationally averaged optical anisotropy () of diphenyl propane, a model analog of bisphenol A polycarbonate, is higher than the corresponding experimental value in the dilute solution phase. The calculations have reproduced the relative trend in the optical anisotropy for the different bisphenyl model compounds in a manner similar to those using semiclassical approach, by incorporation of the condensed phase polarizabilities and quantum chemically calculated geometry structure into the valence optical scheme. Individual contributions to the gas phase polarizability and optical anisotropy of the model compounds for various dihedral conformers, because of the presence of different aliphatic chemical groups, are correctly predicted by the calculations here. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 1092-1100, 2011

}, keywords = {ab initio, bisphenyl, optical anisotropy, polarizability, Polycarbonate, structure}, issn = {0020-7608}, doi = {10.1002/qua.22687}, author = {Sulatha, M. S. and Natarajan, U.} }