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Benoit Champagne - One of the best experts on this subject based on the ideXlab platform.

  • which charge definition for describing the crystal polarizing field and the χ 1 and χ 2 of organic crystals
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Tomasz Seidler, Benoit Champagne
    Abstract:

    The impact of atomic charge definition for describing the crystal polarizing electric field has been assessed in view of predicting the linear and nonlinear optical susceptibilities of Molecular crystals. In this approach, the chromophores are embedded in the electric field of its own point charges, which are evaluated through a self-consistent procedure including charge scaling to account for the screening of the dielectric. Once the crystal field is determined, dressed Molecular Polarizabilities and hyperPolarizabilities are calculated and used as input of an electrostatic interaction scheme to evaluate the crystal linear and nonlinear optical responses. It is observed that many charge definitions (i) based on partitioning the electron density (QTAIM), (ii) obtained by analyzing the quantum-chemical wavefunction (Mulliken, MBS, and NBO), and (iii) derived by fitting to the electrostatic potential (MK, CHelpG, and HLYGAt) give very consistent results and are equally valid whereas Hirshfeld partitioning and CM5 charge parametrizations underestimate the refractive indices and second-order nonlinear optical susceptibilities. An alternative approach omitting charge scaling is demonstrated to overestimate the different crystal optical properties. On the other hand, the molecule embedding approach provides results in close agreement with those calculated with a charge field obtained from periodic boundary condition calculations.

  • natural orbital functional calculations of Molecular Polarizabilities and second hyperPolarizabilities the hydrogen molecule as a test case
    Journal of Physics B, 2014
    Co-Authors: Xabier Lopez, Mario Piris, Masayoshi Nakano, Benoit Champagne
    Abstract:

    The longitudinal polarizability (α) and second hyperpolarizability (γ) of the H2 molecule as a function of the internuclear distance are calculated using the PNOF5 level of theory. It is shown that PNOF5 gives accurate results for the longitudinal α and γ over the whole curve range, even for those structures exhibiting a high degree of diradical character. The good agreement between these results and reference full-CI data highlights the adequacy of PNOF5 to treat electronic systems exhibiting large static electron correlation and shows a promising accuracy in calculating nonlinear optical properties for systems covering a large range of diradical character. The results further support the paradigm of using molecules with intermediate diradical character to enhance the second hyperPolarizabilities.

  • calculating the second order nonlinear optical susceptibilities of 3 methyl 4 nitropyridine n oxide 2 carboxylic acid 4 nitropyridine 1 oxide 2 methyl 4 nitroaniline and m nitroaniline crystals
    International Journal of Quantum Chemistry, 2011
    Co-Authors: Mohammed Benali Kanoun, Benoit Champagne
    Abstract:

    The static and the second harmonic generation second-order nonlinear susceptibilities, χ(2), of 3-methyl-4-nitropyridine N-oxide, 2-carboxylic acid-4-nitropyridine-1-oxide, 2-methyl-4-nitroaniline, and m-nitroaniline crystals are calculated using a model that combines accurate ab initio Molecular properties with an electrostatic interaction approach to account for the crystal packing effects. The impact of the way to distribute the Molecular Polarizabilities on the final second-order nonlinear susceptibilities is highlighted, whereas the frequency dispersion of the macroscopic and Molecular responses is addressed. This approach is shown to reproduce experimental data, at least in what concerns the relative amplitude of χ(2). © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

  • electrostatic modeling of the linear optical susceptibilities of 2 methyl 4 nitroaniline m nitroaniline 3 methyl 4 nitropyridine n oxide and 2 carboxylic acid 4 nitropyridine 1 oxide crystals
    Chemical Physics Letters, 2010
    Co-Authors: Mohammed Benali Kanoun, Edith Botek, Benoit Champagne
    Abstract:

    Abstract An electrostatic interaction scheme is applied to evaluate the macroscopic linear susceptibilities of 2-methyl-4-nitroaniline, m -nitroaniline, 3-methyl-4-nitropyridine N-oxide and 2-carboxylic acid-4-nitropyridine-1-oxide crystals. The Molecular Polarizabilities have been determined from first principles calculations while a distribution scheme is employed to evaluate the Lorentz-factor tensors. It is shown that when employing an appropriate distribution scheme, where the molecules are divided in polarizable sites placed on each heavy atom, this approach reproduces well the experimental crystal linear susceptibilities and its frequency dispersion. Moreover, averaging the Lorentz-factor tensors over the submolecules has only a weak impact on the agreement with experiment.

  • effective Molecular Polarizabilities and hyperPolarizabilities in all trans hexatriene clusters
    Chemical Physics Letters, 2003
    Co-Authors: Edith Botek, Benoit Champagne
    Abstract:

    Abstract Molecular aggregation effects on the static and dynamic electronic polarizability and hyperpolarizability are estimated within the time-dependent Hartree–Fock scheme by using a decomposition procedure over the atomic orbitals. For each molecule, the total property value consists in an algebraic sum of two contributions: an intrinsic part coming only from the atomic orbitals belonging to the molecule and a mixed contribution coming from the crossed terms associated with atomic orbitals describing the target molecule and its neighbors. All- trans hexatriene Molecular clusters are examined to illustrate this decomposition scheme and to analyze the electronic cooperative behavior of the building units.

Mohammed Benali Kanoun - One of the best experts on this subject based on the ideXlab platform.

Edith Botek - One of the best experts on this subject based on the ideXlab platform.

Joseph Zyss - One of the best experts on this subject based on the ideXlab platform.

  • redox switchable second order Molecular Polarizabilities with electron rich iron σ aryl acetylides
    Organometallics, 2002
    Co-Authors: Frederic Paul, Karine Costuas, Isabelle Ledoux, Sandrine Deveau, Joseph Zyss, Jeanfrancois Halet, Claude Lapinte
    Abstract:

    μ·β products were experimentally derived by EFISH for several Fe(II) and Fe(III) σ-aryl acetylides of formula [(η2-dppe)(η5-C5Me5)Fe(C⋮C−Ar)]n+, n(PF6) - (dppe = 1,2-bis(diphenylphosphino)ethane; n = 0, 1), where Ar = p-Py, m-Py, o-Py (1a−c/1a+); Ar = p-C5H4-N(CH3)+, o-C5H4-N(CH3)+ (2a,b+); Ar = p-C6H4X with X = NO2, CN, CF3, H, OMe, NH2 (3a−f/3a−f +). For comparison purposes, EFISH data were also gathered on the Ru(II) analogues (4a,b) of 3a,b. Significant figures for μ·β were determined, with the Fe(II) complexes 2a+ and 3a,b possessing the most electron-deficient aryl rings opposed to the metal center, indicating good second-order Molecular Polarizabilities. For most representatives among 3a−f/3a−f+ and 4a,b, β and β0 values could be derived using DFT-computed dipole moments. The substituent influence on β and β0 is especially marked in the neutral complexes and follows the electron-accepting properties of X:  NO2 > CN > H > OMe ≈ NH2. The comparison between 4a,b and 3a,b indicates that the Fe(II) cent...

  • redox switchable second order Molecular Polarizabilities with electron rich iron σ aryl acetylides
    Organometallics, 2002
    Co-Authors: Frederic Paul, Karine Costuas, Isabelle Ledoux, Sandrine Deveau, Joseph Zyss, Jeanfrancois Halet, Claude Lapinte
    Abstract:

    μ·β products were experimentally derived by EFISH for several Fe(II) and Fe(III) σ-aryl acetylides of formula [(η2-dppe)(η5-C5Me5)Fe(C⋮C−Ar)]n+, n(PF6) - (dppe = 1,2-bis(diphenylphosphino)ethane; n...

  • electronic structure and nonlinear optical properties of push pull polyenes theoretical investigation of benzodithia polyenals and dithiolene polyenals
    Journal of the American Chemical Society, 1992
    Co-Authors: F Meyers, Jeanluc Bredas, Joseph Zyss
    Abstract:

    We report the results of ab initio Hartree-Fock calculations on the geometric and electronic structure and first-order (α) and second-order (β) Molecular Polarizabilities of a series of push-pull polyene molecules. The acceptor is in all cases an aldehyde group while the donor is either a benzodithia, a dithiolene, or a dithiolane group. The benzodithia polyenal compounds have recently been shown to present among the largest μ-β values ever measured. Theoretical results are found to be in excellent agreement with experimental data

Henry A Kurtz - One of the best experts on this subject based on the ideXlab platform.

  • utilizing relativistic effective core potentials for accurate calculations of Molecular Polarizabilities on transition metal compounds
    Journal of Physical Chemistry A, 2006
    Co-Authors: Nicholas P Labello, And Antonio M Ferreira, Henry A Kurtz
    Abstract:

    The requirements necessary to extend an ECP basis set for the calculation of electric and linear optical properties to the transition metals are studied. Previously an augmentation of the SBK basis set for 39 elements with s and p electron only valences (H-Rn, excluding Ga, In, and Tl) [J. Comput. Chem., 2005, 26, 1464-1471] was presented. In this work, electric dipole moments, Polarizabilities, and anisotropies of selected metal hydrides, sulfides, and bromides, cisplatin, and the Fe, Ru, and Os metallocene derivatives along with many other systems are calculated and discussed. ECP calculations of molecules containing 3d and 4d metal centers among main group atoms have good agreement, often within 1-2% of the all-electron result at the time-dependent Hartree-Fock (TDHF)/Sadlej level of theory. Molecules with a 5d metal center have a large difference from and are more accurate than the all-electron results due to the inclusion of relativistic effects in the ECPs. The polarizability as calculated with and without ECPs of metallic clusters and surfaces is increasingly different as atomic number increases, again due to a lack of relativistic effects in the all-electron calculations. The augmented ECP calculations are consistent with relativistic all-electron results, while the Sadlej calculations are consistent with other nonrelativistic results. Both relativistic and basis set effects are less noticeable when the metal is in a formally positive state.

  • an augmented effective core potential basis set for the calculation of Molecular Polarizabilities
    Journal of Computational Chemistry, 2005
    Co-Authors: Nicholas P Labello, Antonio M Ferreira, Henry A Kurtz
    Abstract:

    Calculations of Molecular Polarizabilities require basis sets capable of accurately describing the responses of the electrons to an external perturbation. Unfortunately, basis sets that yield suitable quantitative results have traditionally been all-electron sets with large numbers of primitives, making their use computationally intractable even for moderately sized systems. We present a systematic augmentation of the effective core potential basis set of Stevens et al. [J Chem Phys 81, 12 (1984), Can J Chem 70, 612 (1992)] for 39 main group elements based on the procedure used to construct diffuse and polarization functions in the well-known Sadlej basis sets [Collec Czech Chem Comm 53, 1995 (1988)]. Representative calculations have been performed and we have shown that results to within 1% of all-electron calculations using the Sadlej basis set can be obtained for <1–35% of the computational cost using this new basis set. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1464–1471, 2005