01575nas a2200169   4500008004100000022001400041245015600055210006900211260007100280300001600351490000800367520084100375100001801216700002301234700001601257856013201273       2008                        eng d  a1089-563900aNoniterative density functional response approach: application to nonlinear optical properties of p-nitroaniline and its methyl-substituted derivatives0 aNoniterative density functional response approach application to  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcNOV  a11266-112720 v1123 a<p>We report the effect of substitution, position of the substituent, and the symmetry on the nonlinear optical properties of p-nitroanline (PNA) and its derivatives using our implementation of the noniterative approximation of couple-perturbed Kohn-Sham (CPKS) equation in the deMon2k. Dipole moment, static polarizability, and first hyperpolarizability of these pi-conjugated donor-acceptor organic derivatives of PNA and its methyl-substituted analogs are calculated using our method at different exchange correlation functionals, namely, BP86, BPW91, and BLYP, using 6-31++G** basis set. A comparison of results obtained by our method with those obtained by MP2 (finite-field perturbation) method is presented in this paper. The effect of optical gap on charge transfer and subsequently on polarizabilities has been illustrated.</p>1 aSophy, K., B.1 aShedge, Sapana, V.1 aPal, Sourav  uhttps://library.ncl.res.in/content/noniterative-density-functional-response-approach-application-nonlinear-optical-properties-001731nas a2200169   4500008004100000022001400041245009200055210006900147260007100216300001400287490000600301520107000307100002701377700001801404700001601422856012301438       2012                        eng d  a1549-961800aNOx catalyzed pathway of stratospheric ozone depletion: a coupled cluster investigation0 aNOx catalyzed pathway of stratospheric ozone depletion a coupled  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY  a1895-19010 v83 a<p>We report a theoretical investigation on the NOx catalyzed pathways of stratospheric ozone depletion using highly accurate coupled cluster methods. These catalytic reactions represent a great challenge to state-of-the-art ab initio methods, while their mechanisms remain unclear to both experimentalists and theoreticians. In this work, we have used the so-called ``gold standard of quantum chemistry,'' the CCSD(T) method, to identify the saddle points on NOx-based reaction pathways of ozone hole formation. Energies of the saddle points are calculated using the multireference variants of coupled cluster methods. The calculated activation energies and rate constants show good agreement with available experimental results. Tropospheric precursors to stratospheric NOx radicals have been identified, and their potential importance in stratospheric chemistry has been discussed. Our calculations resolve previous conflicts between ab initio and experimental results for a trans nitro peroxide intermediate, in the NOx catalyzed pathway of ozone depletion.</p>1 aDutta, Achintya, Kumar1 aVaval, Nayana1 aPal, Sourav  uhttps://library.ncl.res.in/content/nox-catalyzed-pathway-stratospheric-ozone-depletion-coupled-cluster-investigation-001795nas a2200169   4500008004100000022001400041245015800055210006900213260008700282300002300369490000800392520103500400100002701435700001801462700001601480856012901496       2015                        eng d  a0021-960600aNew scheme for perturbative triples correction to (0,1) sector of Fock space multi-reference coupled cluster method: Theory, implementation, and examples0 aNew scheme for perturbative triples correction to 01 sector of F  a1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScJAN  aArticle No. 0441130 v1423 a<p>We propose a new elegant strategy to implement third order triples correction in the light of many-body perturbation theory to the Fock space multi-reference coupled cluster method for the ionization problem. The computational scaling as well as the storage requirement is of key concerns in any many-body calculations. Our proposed approach scales as N-6 does not require the storage of triples amplitudes and gives superior agreement over all the previous attempts made. This approach is capable of calculating multiple roots in a single calculation in contrast to the inclusion of perturbative triples in the equation of motion variant of the coupled cluster theory, where each root needs to be computed in a state-specific way and requires both the left and right state vectors together. The performance of the newly implemented scheme is tested by applying to methylene, boron nitride (B2N) anion, nitrogen, water, carbon monoxide, acetylene, formaldehyde, and thymine monomer, a DNA base. (C) 2015 AIP Publishing LLC.</p>1 aDutta, Achintya, Kumar1 aVaval, Nayana1 aPal, Sourav  uhttps://library.ncl.res.in/content/new-scheme-perturbative-triples-correction-01-sector-fock-space-multi-reference-coupled-101360nas a2200157   4500008004100000245008600041210006900127260000800196300001600204490000700220520080100227100001801028700001601046700002601062856011401088       2016                        eng d00aN-2 activation on Al metal clusters: catalyzing role of BN-doped graphene support0 aN2 activation on Al metal clusters catalyzing role of BNdoped gr  cOCT  a27721-277270 v183 aThe successful sustenance of life demands an ambient abiotic process for N-2 activation and dissociation. The Bosch-Haber process remains the only abiotic and synthetic means for N-2 activation and its fixation. Metal nanoclusters have been recently reported for activating molecular nitrogen. Interestingly, the metal clusters explored so far for N-2 activation are free clusters and, hence, are practically not applicable by experimental chemists. Using density functional theory (DFT) based methodology, we propose a potential catalytic system for di-nitrogen activation, viz. supported Al clusters. Al clusters supported on BN doped graphene sheets are seen to activate N-2 molecule with a red shift in the N-N stretching frequency up to 874 cm(-1) with activation barriers as low as 1.14 eV.1 aKumar, Deepak1 aPal, Sourav1 aKrishnamurty, Sailaja  uhttps://library.ncl.res.in/content/n-2-activation-al-metal-clusters-catalyzing-role-bn-doped-graphene-support01790nas a2200181   4500008004100000022001400041245008600055210006900141260000900210300001100219490000700230520118200237100002201419700002201441700001801463700001601481856011101497       2019                        eng d  a2469-992600aNuclear parity- and time-reversal-symmetry violation in the (HgH)-Hg-201 molecule0 aNuclear parity and timereversalsymmetry violation in the HgHHg20  cMAR   a0325030 v993 a<p>Investigation of the nuclear magnetic quadrupole moment (MQM) is an excellent way to reveal the new physics in the hadron sector of matter. Therefore, we investigate the violation of parity (P) and time-reversal (T) invariance induced by the MQM of the( 201) Hg nucleus in the HgH molecule, which has been proposed as a very promising candidate for the experimental search of the electric dipole moment of electron [M. G. Kozlov and A. Derevianko, Phys. Rev. Lett. 97, 063001 (2006)]. We report the precise value of the molecular parameter, W-M, associated with the P, T-odd nuclear MQM-electron interaction in (HgH)-Hg-201 using the four-component relativistic coupled-cluster method. This parameter is required to interpret the experimental P, T-odd frequency shift in terms of the MQM of nuclei. Furthermore, the magnetic hyperfine structure (HFS) constants of the molecule are computed at the same level of theory. We also study the role of core-correlating functions and the virtual energy functions in the calculations of the HFS constant and W-M. The most reliable value of W(M )in HgH is obtained as 3.22 x 10 (33) Hz/e cm (2) with an uncertainty of around 6%.</p>
1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav  uhttps://library.ncl.res.in/content/nuclear-parity-and-time-reversal-symmetry-violation-hgh-hg-201-molecule01908nas a2200181   4500008004100000022001400041245007000055210006700125260000800192300001600200490000800216520132900224100002401553700001501577700001601592700001801608856010001626       2020                        eng d  a1089-563900aNegative ion resonance states: the fock-space coupled-cluster way0 aNegative ion resonance states the fockspace coupledcluster way  cDEC  a10407-104210 v1243 a<p>The negative ion resonance states, which are electron-molecule metastable compound states, play the most important role in free-electron controlled molecular reactions and low-energy free-electron-induced DNA damage. Their electronic structure is often only poorly described but crucial to an understanding of their reaction dynamics. One of the most important challenges to current electronic structure theory is the computation of negative ion resonance states. As a major step forward, coupled-cluster theories, which are well-known for their ability to produce the best approximate bound state electronic eigen solutions, are upgraded to offer the most accurate and effective approximations for negative ion resonance states. The existing Fock-space coupled-cluster (FSCC) and the equation-of-motion coupled-cluster (EOM-CC) approaches that compute bound states are redesigned for the direct and simultaneous determination of both the kinetic energy of the free electron at which the electron-molecule compound states are resonantly formed and the corresponding autodetachment decay rate of the electron from the metastable compound state. This Feature Article reviews the computation of negative ion resonances using the FSCC approach and, in passing, provides the highlights of the equivalent EOM-CC approach.</p>
1 aBasumallick, Suhita1 aSajeev, Y.1 aPal, Sourav1 aVaval, Nayana  uhttps://library.ncl.res.in/content/negative-ion-resonance-states-fock-space-coupled-cluster-way