The Experts below are selected from a list of 47979 Experts worldwide ranked by ideXlab platform
Kurt V Mikkelsen - One of the best experts on this subject based on the ideXlab platform.
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a quantum mechanical method for calculating nonlinear optical properties of condensed phase molecules coupled to a Molecular Mechanics field a quadratic multiconfigurational self consistent field Molecular Mechanics response method
Journal of Chemical Physics, 2001Co-Authors: Tina D Poulsen, Peter R Ogilby, Kurt V MikkelsenAbstract:An approach for determining nonlinear optical properties within a quantum Mechanics/Molecular Mechanics method is presented. The response equations in the multiconfigurational self-consistent-field/Molecular Mechanics approach that includes polarization effects are derived and implemented for second order in response theory. The method is employed to calculate frequency-dependent first hyperpolarizabilities and two-photon absorption properties for H2O in aqueous solution. The results are in close agreement with experimental measurements.
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the combined multiconfigurational self consistent field Molecular Mechanics wave function approach
Journal of Chemical Physics, 2001Co-Authors: Tina D Poulsen, Peter R Ogilby, Jacob Kongsted, Anders Osted, Kurt V MikkelsenAbstract:We present theory and implementation for a new approach for studying solvent effects: the multiconfigurational self-consistent-field/Molecular Mechanics method. With this method it is possible to describe ground, excited, and ionized states of molecules in solution. The approach is tested by investigating the effect of solvent on H2O in aqueous solution. For the calculated energies we find that polarization effects are significant.
R. J. Shannon - One of the best experts on this subject based on the ideXlab platform.
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anharmonic Molecular Mechanics ab initio based morse parametrizations for the popular mm3 force field
Journal of Physical Chemistry A, 2019Co-Authors: R. J. Shannon, B. Hornung, D. P. Tew, D. R. GlowackiAbstract:Methodologies for creating reactive potential energy surfaces from Molecular Mechanics force-fields are becoming increasingly popular. To date, Molecular Mechanics force-fields in biochemistry and small molecule organic chemistry tend to use harmonic expressions to treat bonding stretches, which is a poor approximation in reactive and nonequilibirum Molecular dynamics simulations since bonds are often displaced significantly from their equilibrium positions. For such applications there is need for a better treatment of anharmonicity. In this contribution, Morse bonding potentials have been extensively parametrized for the atom types in the MM3 force field of Allinger and co-workers using high level CCSD(T)(F12*) energies. To our knowledge this is among the first instances of a comprehensive parametrization of Morse potentials in a popular organic chemistry force field. In the context of Molecular dynamics simulations, these data will: (1) facilitate the fitting of reactive potential energy surfaces using ...
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Anharmonic Molecular Mechanics: Ab Initio Based Morse Parametrizations for the Popular MM3 Force Field
2019Co-Authors: R. J. Shannon, B. Hornung, D. P. Tew, D. R. GlowackiAbstract:Methodologies for creating reactive potential energy surfaces from Molecular Mechanics force-fields are becoming increasingly popular. To date, Molecular Mechanics force-fields in biochemistry and small molecule organic chemistry tend to use harmonic expressions to treat bonding stretches, which is a poor approximation in reactive and nonequilibirum Molecular dynamics simulations since bonds are often displaced significantly from their equilibrium positions. For such applications there is need for a better treatment of anharmonicity. In this contribution, Morse bonding potentials have been extensively parametrized for the atom types in the MM3 force field of Allinger and co-workers using high level CCSD(T)(F12*) energies. To our knowledge this is among the first instances of a comprehensive parametrization of Morse potentials in a popular organic chemistry force field. In the context of Molecular dynamics simulations, these data will: (1) facilitate the fitting of reactive potential energy surfaces using empirical valence bond approaches and (2) enable more accurate treatments of energy transfer
Samuel Krimm - One of the best experts on this subject based on the ideXlab platform.
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theoretical basis and accuracy of a non iterative polarization protocol in Molecular Mechanics energy function calculations
Chemical Physics Letters, 2004Co-Authors: Kim Palmo, Samuel KrimmAbstract:The theory of dipole polarization as used in Molecular Mechanics energy functions is analyzed, and the difference in induction energy between an iterative (self-consistent) and non-iterative (one-step) scheme is derived. It is concluded that this difference is bound to be small in most cases, so that a non-iterative polarization model can be expected to give a satisfactory representation of the induction energy. This is demonstrated with examples of configurations of water molecules. The advantages of a one-step procedure are discussed.
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a spectroscopically effective Molecular Mechanics model for the interMolecular interactions of the hydrogen bonded n methylacetamide dimer
Chemical Physics Letters, 1999Co-Authors: Weili Qian, Noemi G Mirkin, Samuel KrimmAbstract:Abstract An MP2/6-31+G ∗ calculation of the N -methylacetamide dimer shows that it has two minimum energy structures, both hydrogen bonded with peptide planes roughly perpendicular to each other. A complete Molecular Mechanics optimization of the dimer has been done, using a model for the interMolecular interactions consisting of charges, atomic dipoles, and van der Waals interactions and the methodology of our spectroscopically determined force field for the intraMolecular interactions. The two structures are satisfactorily reproduced, as are their interaction energies, their dipole moments, and, from the point of view of our goal of a spectroscopically accurate force field, their six interMolecular normal mode frequencies.
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construction of Molecular Mechanics energy functions by mathematical transformation of ab initio force fields and structures
Journal of Computational Chemistry, 1991Co-Authors: Kim Palmo, Larsolof Pietila, Samuel KrimmAbstract:A method is presented by which ab initio (or empirical) force fields and structures can be converted to Molecular Mechanics energy parameters. Using Cartesian coordinates, the effect of van der Waals and other nonquadratic interactions is eliminated from the original spectroscopic force field, and Molecular Mechanics force constants and reference geometry parameters are derived. The computed parameters yield Molecular structure and vibrational frequencies that are identical to the original ones. The transformation produces a complete general valence force field, which in most cases is impractical, and a procedure to reduce the number of force constants is therefore described. Different ways of applying the transformation are outlined.
D. R. Glowacki - One of the best experts on this subject based on the ideXlab platform.
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anharmonic Molecular Mechanics ab initio based morse parametrizations for the popular mm3 force field
Journal of Physical Chemistry A, 2019Co-Authors: R. J. Shannon, B. Hornung, D. P. Tew, D. R. GlowackiAbstract:Methodologies for creating reactive potential energy surfaces from Molecular Mechanics force-fields are becoming increasingly popular. To date, Molecular Mechanics force-fields in biochemistry and small molecule organic chemistry tend to use harmonic expressions to treat bonding stretches, which is a poor approximation in reactive and nonequilibirum Molecular dynamics simulations since bonds are often displaced significantly from their equilibrium positions. For such applications there is need for a better treatment of anharmonicity. In this contribution, Morse bonding potentials have been extensively parametrized for the atom types in the MM3 force field of Allinger and co-workers using high level CCSD(T)(F12*) energies. To our knowledge this is among the first instances of a comprehensive parametrization of Morse potentials in a popular organic chemistry force field. In the context of Molecular dynamics simulations, these data will: (1) facilitate the fitting of reactive potential energy surfaces using ...
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Anharmonic Molecular Mechanics: Ab Initio Based Morse Parametrizations for the Popular MM3 Force Field
2019Co-Authors: R. J. Shannon, B. Hornung, D. P. Tew, D. R. GlowackiAbstract:Methodologies for creating reactive potential energy surfaces from Molecular Mechanics force-fields are becoming increasingly popular. To date, Molecular Mechanics force-fields in biochemistry and small molecule organic chemistry tend to use harmonic expressions to treat bonding stretches, which is a poor approximation in reactive and nonequilibirum Molecular dynamics simulations since bonds are often displaced significantly from their equilibrium positions. For such applications there is need for a better treatment of anharmonicity. In this contribution, Morse bonding potentials have been extensively parametrized for the atom types in the MM3 force field of Allinger and co-workers using high level CCSD(T)(F12*) energies. To our knowledge this is among the first instances of a comprehensive parametrization of Morse potentials in a popular organic chemistry force field. In the context of Molecular dynamics simulations, these data will: (1) facilitate the fitting of reactive potential energy surfaces using empirical valence bond approaches and (2) enable more accurate treatments of energy transfer
Tina D Poulsen - One of the best experts on this subject based on the ideXlab platform.
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a quantum mechanical method for calculating nonlinear optical properties of condensed phase molecules coupled to a Molecular Mechanics field a quadratic multiconfigurational self consistent field Molecular Mechanics response method
Journal of Chemical Physics, 2001Co-Authors: Tina D Poulsen, Peter R Ogilby, Kurt V MikkelsenAbstract:An approach for determining nonlinear optical properties within a quantum Mechanics/Molecular Mechanics method is presented. The response equations in the multiconfigurational self-consistent-field/Molecular Mechanics approach that includes polarization effects are derived and implemented for second order in response theory. The method is employed to calculate frequency-dependent first hyperpolarizabilities and two-photon absorption properties for H2O in aqueous solution. The results are in close agreement with experimental measurements.
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the combined multiconfigurational self consistent field Molecular Mechanics wave function approach
Journal of Chemical Physics, 2001Co-Authors: Tina D Poulsen, Peter R Ogilby, Jacob Kongsted, Anders Osted, Kurt V MikkelsenAbstract:We present theory and implementation for a new approach for studying solvent effects: the multiconfigurational self-consistent-field/Molecular Mechanics method. With this method it is possible to describe ground, excited, and ionized states of molecules in solution. The approach is tested by investigating the effect of solvent on H2O in aqueous solution. For the calculated energies we find that polarization effects are significant.