Differential Overlap

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Michael C. Zerner - One of the best experts on this subject based on the ideXlab platform.

  • Projected Unrestricted Hartree-Fock Calculations within the Intermediate Neglect of Differential Overlap Model
    Journal of Physical Chemistry A, 1999
    Co-Authors: Marshall G Cory, Michael C. Zerner
    Abstract:

    We develop a stable scheme for full spin projection of an unrestricted Hartree−Fock wave function using ideas originally discussed by Lowdin and Harriman. We examine three test cases within the intermediate neglect of Differential Overlap/spectroscopic method (INDO/S); a model of ferredoxin, Fe−S enzyme models for nitratases, and Ni6 clusters. The projected INDO/S UHF method has a remarkable ability to predict spin multiplicities correctly and with far greater ease than corresponding restricted open-shell Hartree−Fock calculations followed by configuration interaction (ROHF/CI).

  • Extension of the Neglect of Diatomic Differential Overlap Method to Spectroscopy. NDDO-G Parametrization and Results for Organic Molecules
    The Journal of Physical Chemistry A, 1999
    Co-Authors: Alexander A. Voityuk, Michael C. Zerner, Notker Rösch
    Abstract:

    A new semiempirical scheme, referred to as NDDO-G, for calculating geometries and spectroscopic properties of molecules, is described. The method is based on the NDDO (neglect of diatomic Differential Overlap) approximation. It uses the point-charge model and the Mataga−Nishimoto formula to evaluate two-center two-electron integrals. The NDDO-G model has been parametrized for the elements H, C, N, and O. Molecular geometries of organic molecules are well predicted by NDDO-G; for 60 molecules, the mean absolute error of bond lengths is 0.014 A and that of bond angles is 1.9°. The spectroscopic variant of the NDDO-G scheme provides electronic excitations using configuration interaction of singly excited states (CIS). It has been applied to calculate absorption spectra (vertical transitions) of several dozens organic molecules and photoelectron spectra within Koopmans' approximation. These NDDO-G results are compared with experimental results and with results of high-level ab initio calculations. The mean ab...

  • Intermediate Neglect of Differential Overlap Calculations on the Electronic Spectra of Transition Metal Complexes
    Metal-Ligand Interactions, 1996
    Co-Authors: Michael C. Zerner
    Abstract:

    The title of this manuscript really suggests three separate subjects:(l) The Intermediate Neglect of Differential Overlap Model (INDO/S) that we have used for many years to describe the electronic spectraand photochemistry of large systems, (2) the description of how one might calculate electronic spectroscopy,and finally, (3) the electronic structure of transition metal complexes, per se. I should like to begin with the third of these, which is the theme of this school, paying only cursory attention to the first two. Transition metal compounds are different from compounds that contain only main group elements,and I think it is interesting to examine why. A after all, there are rather good computational tools for examining the electronic structure of molecules that do not contain transition metal compounds that are now widely used by theoristsand experimentalists alike. So called ab-initio programs such as Gaussian92 [1], GAMES S [2], Turbomole [3], ACESII [4], are rather sophisticated packages that yield accurate results for smaller systems,AMPAC [5], MOPAC [6], ZINDO [7]and SINDO [8] are semi-empirical methods available for rather large systems,and there are molecular modeling methods that use classical force fields such as AMBER [9], CHARM [10]and INSIGHT [11] that can be used for thousands of atoms. Such programs have not been widely used in the study of transition metal compounds. Why is that?

  • An intermediate neglect of Differential Overlap technique for actinide compounds
    The Journal of Chemical Physics, 1994
    Co-Authors: Marshall G Cory, Manfred Kotzian, Notker Rösch, Sibylle Köstlmeier, Michael C. Zerner
    Abstract:

    An intermediate neglect of Differential Overlap method for examining the electronic structure of actinide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac–Fock atomic calculations, the inclusion of all one‐center two‐electron integrals, and a parameter set based on molecular geometry and ionization spectra. The model is successful in reproducing the geometries of many small test molecules, especially the hexahalides and tetrahalides of the early actinides. We also investigate the bonding in actinocenes and the photoelectron spectra of pentavalent uranium amide/imide complexes as two diverse examples in which this model can be used to help in understanding and prediction.

  • Calculation of 13C‐NMR chemical shift using the intermediate neglect of Differential Overlap model
    International Journal of Quantum Chemistry, 1992
    Co-Authors: John David Baker, Michael C. Zerner
    Abstract:

    The local origin/local orbital (LORG) method of Hansen and Bouman has been implemented with the intermediate neglect of Differential Overlap Hamiltonian for spectroscopy (INDO/S). The method is shown capable of demonstrating the inductive effects associated with electron-withdrawing substituents through the diamagnetic shielding term. In addition, the method is capable of differentiating chemical shift in differing bond environments. The calculated paramagnetic contribution, however, is deficient for substituents that saturate the minimal basis such as oxygen and fluorine, which severely limits the general utility of the procedure. Through the utilization of reduced linear equations for the paramagnetic term, the method is amenable to any molecule for which a self-consistent field can be performed and therefore can potentially be used to study very large systems. At present, however, the LORG method when used with the rapid INDO/S model Hamiltonian does not reliably reproduce the paramagnetic contribution to the shielding.

Donald G Truhlar - One of the best experts on this subject based on the ideXlab platform.

  • polarized molecular orbital model chemistry ii the pmo method
    Journal of Chemical Theory and Computation, 2011
    Co-Authors: Peng Zhang, Luke Fiedler, Hannah R Leverentz, Donald G Truhlar
    Abstract:

    We present a new semiempirical molecular orbital method based on neglect of diatomic Differential Overlap. This method differs from previous NDDO-based methods in that we include p orbitals on hydr...

  • Energies, geometries, and charge distributions of ZN molecules, clusters, and biocenters from coupled cluster, density functional, and neglect of diatomic Differential Overlap models
    Journal of chemical theory and computation, 2009
    Co-Authors: Anastassia Sorkin, Donald G Truhlar, Elizabeth A. Amin
    Abstract:

    We present benchmark databases of Zn-ligand bond distances, bond angles, dipole moments, and bond dissociation energies for Zn-containing small molecules and Zn coordination compounds with H, CH3, C2H5, NH3, O, OH, H2O, F, Cl, S, and SCH3 ligands. The test set also includes clusters with Zn-Zn bonds. In addition, we calculated dipole moments and binding energies for Zn centers in coordination environments taken from zinc metalloenzyme X-ray structures, representing both structural and catalytic zinc centers. The benchmark values are based on relativistic-core coupled cluster calculations. These benchmark calculations are used to test the predictions of four density functionals, namely B3LYP and the more recently developed M05-2X, M06, and M06-2X levels of theory, and six semiempirical methods, including neglect of diatomic Differential Overlap (NDDO) calculations incorporating the new PM3 parameter set for Zn called ZnB, developed by Brothers and co-workers, and the recent PM6 parametrization of Stewart. We found that the best DFT method to reproduce dipole moments and dissociation energies of our Zn compound database is M05-2X, which is consistent with a previous study employing a much smaller and less diverse database and a much larger set of density functionals. Here we show that M05-2X geometries and single-point coupled cluster calculations with M05-2X geometries can also be used as benchmarks for larger compounds, where coupled cluster optimization is impractical, and in particular we use this strategy to extend the geometry, binding energy, and dipole moment databases to additional molecules, and we extend the tests involving crystal-site coordination compounds to two additional proteins. We find that the most predictive NDDO methods for our training set are PM3 and MNDO/d. Notably, we also find large errors in B3LYP for the coordination compounds based on experimental X-ray geometries.

  • A Universal Solvation Model Based on Class IV Charges and the Intermediate Neglect of Differential Overlap for the Spectroscopy Molecular Orbital Method
    The Journal of Physical Chemistry A, 2000
    Co-Authors: Tianhai Zhu, Christopher J. Cramer, Donald G Truhlar
    Abstract:

    The SM5.42R solvation model, which is based on SM5-type atomic surface tensions, class IV point charges based on charge model 2, and rigid geometries, is parametrized for the intermediate neglect of Differential Overlap for spectroscopy (INDO/S) method, both in the original (INDO/S) and more recent (INDO/S2) versions. The parametrization is based on 2184 free energies of solvation of 275 neutral solutes and 49 ions in water and 90 organic solvents.

  • Direct dynamics calculations with NDDO (neglect of diatomic Differential Overlap) molecular orbital theory with specific reaction parameters
    The Journal of Physical Chemistry, 1991
    Co-Authors: Àngels González-lafont, Thanh N. Truong, Donald G Truhlar
    Abstract:

    The authors have calculated the {alpha}-deuterium secondary kinetic isotope effect and the heavy-water solvent kinetic isotope effect for the reaction Cl{sup {minus}}(H{sub 2}O){sub n} + CH{sub 3}Cl{prime} {yields} CH{sub 3}Cl + Cl{prime}{sup {minus}}(H{sub 2}O){sub n} with n = 0, 1, and 2. Instead of using an analytic potential energy function, they calculated the energy and gradient whenever they needed them by neglect of diatomic Differential Overlap (NDDO) molecular orbital theory with parameters adjusted specifically for these individual reactions. The interface of the molecular orbital calculations with the dynamics calculations was accomplished by the use of a new direct dynamics computer program MORATE. The results are compared in detail to previous calculations based on 18-, 27-, and 36-dimensional semiglobal analytic potential energy functions, and the correspondences between the kinetic isotope effects and their interpretation in terms of specific modes are very encouraging. They conclude that use of NDDO molecular orbital theory with specific reaction parameters should be a very useful technique for modeling potential energy surfaces for polyatomic reactions. 69 refs., 6 figs., 13 tabs.

Notker Rösch - One of the best experts on this subject based on the ideXlab platform.

  • Extension of the Neglect of Diatomic Differential Overlap Method to Spectroscopy. NDDO-G Parametrization and Results for Organic Molecules
    The Journal of Physical Chemistry A, 1999
    Co-Authors: Alexander A. Voityuk, Michael C. Zerner, Notker Rösch
    Abstract:

    A new semiempirical scheme, referred to as NDDO-G, for calculating geometries and spectroscopic properties of molecules, is described. The method is based on the NDDO (neglect of diatomic Differential Overlap) approximation. It uses the point-charge model and the Mataga−Nishimoto formula to evaluate two-center two-electron integrals. The NDDO-G model has been parametrized for the elements H, C, N, and O. Molecular geometries of organic molecules are well predicted by NDDO-G; for 60 molecules, the mean absolute error of bond lengths is 0.014 A and that of bond angles is 1.9°. The spectroscopic variant of the NDDO-G scheme provides electronic excitations using configuration interaction of singly excited states (CIS). It has been applied to calculate absorption spectra (vertical transitions) of several dozens organic molecules and photoelectron spectra within Koopmans' approximation. These NDDO-G results are compared with experimental results and with results of high-level ab initio calculations. The mean ab...

  • An intermediate neglect of Differential Overlap technique for actinide compounds
    The Journal of Chemical Physics, 1994
    Co-Authors: Marshall G Cory, Manfred Kotzian, Notker Rösch, Sibylle Köstlmeier, Michael C. Zerner
    Abstract:

    An intermediate neglect of Differential Overlap method for examining the electronic structure of actinide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac–Fock atomic calculations, the inclusion of all one‐center two‐electron integrals, and a parameter set based on molecular geometry and ionization spectra. The model is successful in reproducing the geometries of many small test molecules, especially the hexahalides and tetrahalides of the early actinides. We also investigate the bonding in actinocenes and the photoelectron spectra of pentavalent uranium amide/imide complexes as two diverse examples in which this model can be used to help in understanding and prediction.

  • Intermediate neglect of Differential Overlap spectroscopic studies on lanthanide complexes
    Theoretical Chemistry Accounts, 1992
    Co-Authors: Manfred Kotzian, Notker Rösch, Michael C. Zerner
    Abstract:

    The Intermediate Nelgect of Differential Overlap model for spectroscopy has been extended to lanthanide complexes by including spin-orbit coupling. The method uses atomic spectroscopy and model Dirac-Fock calculations on the lanthanide atoms and ions to obtain ionization potentials, Slater-Condon factors and basis sets. The spin-orbit interaction strength, ζ(nl), is acquired from atomic spectroscopy, and only one-center terms are formally included. Calculation then proceeds using one open-shell operator for all sevenf-orbitals initially assumed degenerate to generate starting non-relativistic molecular orbitals for the subsequent configuration-interaction and spin-orbit calculation.

  • Intermediate neglect of Differential Overlap spectroscopic studies on lanthanide complexes
    Theoretica chimica acta, 1992
    Co-Authors: Manfred Kotzian, Notker Rösch, Michael C. Zerner
    Abstract:

    The Intermediate Nelgect of Differential Overlap model for spectroscopy has been extended to lanthanide complexes by including spin-orbit coupling. The method uses atomic spectroscopy and model Dirac-Fock calculations on the lanthanide atoms and ions to obtain ionization potentials, Slater-Condon factors and basis sets. The spin-orbit interaction strength, ζ( nl ), is acquired from atomic spectroscopy, and only one-center terms are formally included. Calculation then proceeds using one open-shell operator for all seven f -orbitals initially assumed degenerate to generate starting non-relativistic molecular orbitals for the subsequent configuration-interaction and spin-orbit calculation. Calculations are performed on the monoxides La, Ce, Gd, and Lu where there are ample experimental assignments. In general, the results are quite good, suggesting that the calculated energies, oscillator strengths and spin-orbit splittings can be used with success in assigning spectra, even in those cases where jj -coupling is of intermediate strength.

  • Intermediate neglect of Differential Overlap spectroscopic studies of lanthanide complexes: Diatomic lanthanide oxides PrO and TmO
    Journal of Molecular Spectroscopy, 1991
    Co-Authors: Manfred Kotzian, Notker Rösch
    Abstract:

    Abstract The low-lying states of PrO and TmO arising from the atomic-like molecular ground states 4 f 2 6 s and 4 f 12 6 s , respectively, are calculated employing a spectroscopic intermediate neglect of Differential Overlap (INDO) molecular orbital procedure augmented by a double-group configuration interaction (CI) technique which includes spin-orbit interactions. The molecular states closely follow the coupling pattern of the atomic states, as is revealed in a display according to the approximate quantum number J a characterizing the total angular momentum number of the lanthanide contribution to the leading determinant. Overall agreement with experiment and recent ligand field calculations is very good, especially for the manifold of the lowest-lying multiplet component of PrO ( J f =4). Both theoretical procedures reproduce the experimental ω value for the ground state, 3.5. However, the INDO approach predicts a different ω for the ground state of TmO than do ligand field calculations.

Alexander A. Voityuk - One of the best experts on this subject based on the ideXlab platform.

  • Intermediate neglect of Differential Overlap for spectroscopy
    Wiley Interdisciplinary Reviews: Computational Molecular Science, 2013
    Co-Authors: Alexander A. Voityuk
    Abstract:

    Intermediate neglect of Differential Overlap for spectroscopy is a semiempirical approach, which is widely used to calculate spectroscopic and electron-transfer properties of various molecular systems including biological molecules, transition metal compounds, and advanced materials. In the review, we consider the computational scheme of the method and its recent applications in chemistry, biophysics, and material science. © 2013 John Wiley & Sons, Ltd.

  • Extension of the Neglect of Diatomic Differential Overlap Method to Spectroscopy. NDDO-G Parametrization and Results for Organic Molecules
    The Journal of Physical Chemistry A, 1999
    Co-Authors: Alexander A. Voityuk, Michael C. Zerner, Notker Rösch
    Abstract:

    A new semiempirical scheme, referred to as NDDO-G, for calculating geometries and spectroscopic properties of molecules, is described. The method is based on the NDDO (neglect of diatomic Differential Overlap) approximation. It uses the point-charge model and the Mataga−Nishimoto formula to evaluate two-center two-electron integrals. The NDDO-G model has been parametrized for the elements H, C, N, and O. Molecular geometries of organic molecules are well predicted by NDDO-G; for 60 molecules, the mean absolute error of bond lengths is 0.014 A and that of bond angles is 1.9°. The spectroscopic variant of the NDDO-G scheme provides electronic excitations using configuration interaction of singly excited states (CIS). It has been applied to calculate absorption spectra (vertical transitions) of several dozens organic molecules and photoelectron spectra within Koopmans' approximation. These NDDO-G results are compared with experimental results and with results of high-level ab initio calculations. The mean ab...

Manfred Kotzian - One of the best experts on this subject based on the ideXlab platform.

  • An intermediate neglect of Differential Overlap technique for actinide compounds
    The Journal of Chemical Physics, 1994
    Co-Authors: Marshall G Cory, Manfred Kotzian, Notker Rösch, Sibylle Köstlmeier, Michael C. Zerner
    Abstract:

    An intermediate neglect of Differential Overlap method for examining the electronic structure of actinide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac–Fock atomic calculations, the inclusion of all one‐center two‐electron integrals, and a parameter set based on molecular geometry and ionization spectra. The model is successful in reproducing the geometries of many small test molecules, especially the hexahalides and tetrahalides of the early actinides. We also investigate the bonding in actinocenes and the photoelectron spectra of pentavalent uranium amide/imide complexes as two diverse examples in which this model can be used to help in understanding and prediction.

  • Intermediate neglect of Differential Overlap spectroscopic studies on lanthanide complexes
    Theoretical Chemistry Accounts, 1992
    Co-Authors: Manfred Kotzian, Notker Rösch, Michael C. Zerner
    Abstract:

    The Intermediate Nelgect of Differential Overlap model for spectroscopy has been extended to lanthanide complexes by including spin-orbit coupling. The method uses atomic spectroscopy and model Dirac-Fock calculations on the lanthanide atoms and ions to obtain ionization potentials, Slater-Condon factors and basis sets. The spin-orbit interaction strength, ζ(nl), is acquired from atomic spectroscopy, and only one-center terms are formally included. Calculation then proceeds using one open-shell operator for all sevenf-orbitals initially assumed degenerate to generate starting non-relativistic molecular orbitals for the subsequent configuration-interaction and spin-orbit calculation.

  • Intermediate neglect of Differential Overlap spectroscopic studies on lanthanide complexes
    Theoretica chimica acta, 1992
    Co-Authors: Manfred Kotzian, Notker Rösch, Michael C. Zerner
    Abstract:

    The Intermediate Nelgect of Differential Overlap model for spectroscopy has been extended to lanthanide complexes by including spin-orbit coupling. The method uses atomic spectroscopy and model Dirac-Fock calculations on the lanthanide atoms and ions to obtain ionization potentials, Slater-Condon factors and basis sets. The spin-orbit interaction strength, ζ( nl ), is acquired from atomic spectroscopy, and only one-center terms are formally included. Calculation then proceeds using one open-shell operator for all seven f -orbitals initially assumed degenerate to generate starting non-relativistic molecular orbitals for the subsequent configuration-interaction and spin-orbit calculation. Calculations are performed on the monoxides La, Ce, Gd, and Lu where there are ample experimental assignments. In general, the results are quite good, suggesting that the calculated energies, oscillator strengths and spin-orbit splittings can be used with success in assigning spectra, even in those cases where jj -coupling is of intermediate strength.

  • Intermediate neglect of Differential Overlap spectroscopic studies of lanthanide complexes: Diatomic lanthanide oxides PrO and TmO
    Journal of Molecular Spectroscopy, 1991
    Co-Authors: Manfred Kotzian, Notker Rösch
    Abstract:

    Abstract The low-lying states of PrO and TmO arising from the atomic-like molecular ground states 4 f 2 6 s and 4 f 12 6 s , respectively, are calculated employing a spectroscopic intermediate neglect of Differential Overlap (INDO) molecular orbital procedure augmented by a double-group configuration interaction (CI) technique which includes spin-orbit interactions. The molecular states closely follow the coupling pattern of the atomic states, as is revealed in a display according to the approximate quantum number J a characterizing the total angular momentum number of the lanthanide contribution to the leading determinant. Overall agreement with experiment and recent ligand field calculations is very good, especially for the manifold of the lowest-lying multiplet component of PrO ( J f =4). Both theoretical procedures reproduce the experimental ω value for the ground state, 3.5. However, the INDO approach predicts a different ω for the ground state of TmO than do ligand field calculations.