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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the sign reversal of the second-order molecular polarizability in polymethineimine chains (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 6766-6774 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The second-order polarizability tensor (β) components of polymethineimine oligomers have been computed with the semiempirical intermediate neglect of differential overlap (INDO) coupled either to sum-over-states (SOS) or finite-field real space approach. Our goal is to rationalize the sign reversal of the longitudinal β component with chain length. The INDO results are shown to compare well with the values obtained from previous ab initio calculations. Using a four-state SOS model that reproduces correctly the evolution of β with chain length, we demonstrate that the shape of the β curve can be explained as resulting from the competition between two contributions of opposite signs. In the framework of a real-space approach, those contributions are found to correspond to bond charge and bond polarization phenomena. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1401822
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  • 2
    Electronic Resource
    Electronic Resource
    Comment on "Calculation of ab initio dynamic hyperpolarizabilities of polymers" [J. Chem. Phys. 110, 2717 (1999)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1616-1617 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We evaluate the static and dynamic electronic longitudinal polarizability and first hyperpolarizability of infinite poly-water by using the same geometry, the same orientation and the same basis set as Otto et al. but by applying the finite oligomer technique. We show that for the first hyperpolarizability, the polymeric values per unit cell calculated by Otto et al. are inconsistent by several orders of magnitude with respect to the infinite oligomer limit. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480727
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  • 3
    Electronic Resource
    Electronic Resource
    Long-range effects in optimizing the geometry of stereoregular polymers. II. Hydrogen fluoride chains as a working example (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5324-5330 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use linear hydrogen fluoride chains to evaluate the efficiency of the long-range approach developed in the first paper of this series. A wide panel of tests and comparisons are carried out in order to understand the influence of the parameters on the quality of the forces and the accuracy of the optimized geometry. The long-range corrections are demonstrated to be essential for tight optimizations as well as to fasten the calculation procedure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479791
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  • 4
    Electronic Resource
    Electronic Resource
    Long-range effects in optimizing the geometry of stereoregular polymers. I. Formalism (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5306-5323 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop an original methodology to calculate analytically the long-range (LR) Coulombic effects to be included in Hartree–Fock forces computed on stereoregular polymers. The technique presented, based on multiple Taylor series expansions, is completely general and can be easily extended to all orders of expansion and to geometrical derivatives of higher order. In the McMurchie Davidson or similar schemes, the LR terms are added directly to Hermite integrals and LR effects are naturally considered during the computation of the energy and its derivatives. Each type of derivative (nuclear-repulsion energy, overlap and kinetic energy integrals, electron–nuclear attraction and two-electron integrals) is examined to quantify the impact of LR corrections. It turns out that the lattice sums of the gradients evaluated on a model macromolecule converge much faster when including those corrections. In addition, the dependence of the energy with respect to the unit cell length is for the first time considered in full details. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479790
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  • 5
    Electronic Resource
    Electronic Resource
    Ab initio static polarizability and first hyperpolarizability of model polymethineimine chains. II. Effects of conformation and of substitution by donor/acceptor end groups (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 5076-5087 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An ab initio coupled Hartree–Fock study has been carried out on polymethineimine (PMI) oligomers with an increasing number of unit cells (up to N=20) to determine the effect of conformational differences, and of end-capping by a strong donor-acceptor pair, on the static electronic longitudinal polarizability (αL) and first hyperpolarizability (βL). For the unsubstituted polymer the differences in βL per unit cell among the four conformations examined—trans-transoïd (TT), cis-transoïd (CT), trans-cisoïd (TC) and helical (HEL)—are large. βL/N is positive for the CT polymer, in contrast with the other conformers and with μL/N, which is negative in all cases. The TC polymer has the largest |βL|/N despite having a relatively small αL/N. Substitution of a strong acceptor (NO2) at the carbon end of an oligomer and a strong donor (NH2) at the nitrogen end results in a large increase of βL/N for small/medium N. In the case of the TT and, particularly, the CT conformer this leads to a maximum in |βL|/N vs N at N=4–6, which is substantially greater in magnitude than the one at N=∞. The latter is unaffected by substitution. We compare the [βL(N)/N]max obtained at intermediate N for substituted PMI chains with those calculated for linear polyenes and other π-conjugated oligomers. The shape of all the βL/N vs N curves obtained is fit to a function which yields parameters characterizing the delocalization along the backbone, the unit cell asymmetry, and the asymmetry of the chain ends.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474892
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  • 6
    Electronic Resource
    Electronic Resource
    Ab initio band structure of polymethineimine isomers (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1023-1030 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio crystal orbital calculations have been performed on stereoregular polymethineimine (PMI) at the restricted Hartree-Fock/6-31G level. Since the optimized geometries of the parent oligomers show only small energy differences, four isomers, namely, trans-transoïd (TT), cis-transoïd (CT), trans-cisoïd (TC) and helical (HEL) have been studied to point out the geometry-dependences of the band structure, density of states (DOS) and polarizability. Some of these could be helpful for identifying the isomers. It turns out that the DOS makes the TT and CT isomers distinguishable, whereas the TC and HEL isomers present very similar DOS. Moreover, it is shown that the longitudinal polarizability per unit cell increases in the order HEL, TC, CT and TT. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475497
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  • 7
    Electronic Resource
    Electronic Resource
    Electron nuclear dynamics of proton collisions with methane at 30 eV (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6146-6155 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reactive collisions of protons with methane molecules at 30 eV in the laboratory frame are studied with the electron nuclear dynamics (END). The results from this theoretical approach, which does not invoke the Born–Oppenheimer approximation and does not impose any constraints on the nuclear dynamics, are compared to the results from time-of-flight measurements. Total differential cross sections and integral cross sections as well as fragmentation ratios and energy loss spectra are discussed.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474343
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  • 8
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    Effect of the cation model on the equilibrium structure of poly-L-glutamate in aqueous sodium chloride solution (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-12-15
    Description: We demonstrate that different sets of Lennard-Jones parameters proposed for the Na + ion, in conjunction with the empirical combining rules routinely used in simulation packages, can lead to essentially different equilibrium structures for a deprotonated poly-L-glutamic acid molecule (poly-L-glutamate) dissolved in a 0.3M aqueous NaCl solution. It is, however, difficult to discriminate a priori between these model potentials; when investigating the structure of the Na + -solvation shell in bulk NaCl solution, all parameter sets lead to radial distribution functions and solvation numbers in broad agreement with the available experimental data. We do not find any such dependency of the equilibrium structure on the parameters associated with the Cl − ion. This work does not aim at recommending a particular set of parameters for any particular purpose. Instead, it stresses the model dependence of simulation results for complex systems such as biomolecules in solution and thus the difficulties if simulations are to be used for unbiased predictions, or to discriminate between contradictory experiments. However, this opens the possibility of validating a model specifically in view of analyzing experimental data believed to be reliable.
    Electronic ISSN: 1931-9223
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 9
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    Effect of the cation model on the equilibrium structure of poly-L-glutamate in aqueous sodium chloride solution (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-12-15
    Description: We demonstrate that different sets of Lennard-Jones parameters proposed for the Na + ion, in conjunction with the empirical combining rules routinely used in simulation packages, can lead to essentially different equilibrium structures for a deprotonated poly-L-glutamic acid molecule (poly-L-glutamate) dissolved in a 0.3M aqueous NaCl solution. It is, however, difficult to discriminate a priori between these model potentials; when investigating the structure of the Na + -solvation shell in bulk NaCl solution, all parameter sets lead to radial distribution functions and solvation numbers in broad agreement with the available experimental data. We do not find any such dependency of the equilibrium structure on the parameters associated with the Cl − ion. This work does not aim at recommending a particular set of parameters for any particular purpose. Instead, it stresses the model dependence of simulation results for complex systems such as biomolecules in solution and thus the difficulties if simulations are to be used for unbiased predictions, or to discriminate between contradictory experiments. However, this opens the possibility of validating a model specifically in view of analyzing experimental data believed to be reliable.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 10
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    Combining the GW formalism with the polarizable continuum model: A state-specific non-equilibrium approach (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-04-26
    Description: We have implemented the polarizable continuum model within the framework of the many-body Green’s function GW formalism for the calculation of electron addition and removal energies in solution. The present formalism includes both ground-state and non-equilibrium polarization effects. In addition, the polarization energies are state-specific, allowing to obtain the bath-induced renormalisation energy of all occupied and virtual energy levels. Our implementation is validated by comparisons with ΔSCF calculations performed at both the density functional theory and coupled-cluster single and double levels for solvated nucleobases. The present study opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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