Optimization of parameters for semiempirical methods I. Method

Stewart, James J. P.

doi:10.1002/jcc.540100208

Cited by 7,736 publications

(3,639 citation statements)

References 18 publications

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“…Many of the parameters have been re-fitted 39 and thus differ slightly from their original values. 10 In addition, the screening function (and thus the integrals) in the terms differ from those in the parent methods. Diagonalization of the associated Fock matrix yields the self-consistent problem which is solved variationally for the electron and polarization density matrices.…”

Section: Overview Of Scp-nddo Theorymentioning

confidence: 99%

“…A pairwise core repulsion function was added to MNDO in the MNDO/H, 23 MNDO/GH, 24 MNDO/M, 25,26 and I-MNDO 27 methods. After MNDO, the newer AM1, 9 PM3, 10 In ref 39 some of us introduced a different correction approach. The self-consistent polarization (SCP) approach uses an auxiliary charge density (modeled by one or at most a few Gaussian centers placed on atomic sites) which supplements the NDDO or DFT charge densities and is used to better describe the intermolecular interaction.…”

Section: Introductionmentioning

confidence: 99%

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Semiempirical Self-Consistent Polarization Description of Bulk Water, the Liquid−Vapor Interface, and Cubic Ice

et al. 2011

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We have applied an efficient electronic structure approach, the semiempirical self-consistent polarization neglect of diatomic differential overlap (SCP-NDDO) method, previously parametrized to reproduce properties of water clusters by Chang, Schenter, and Garrett J. Chem. Phys. 2008, 128, 164111] and now implemented in the CP2K package, to model ambient liquid water at 300 K (both the bulk and the liquid-vapor interface) and cubic ice at 15 and 250 K The SCP-NDDO potential retains its transferability and good performance across the full range of conditions encountered in the clusters and the bulk phases of water. In particular, we obtain good results for the density, radial distribution functions, enthalpy of vaporization, self-diffusion coefficient, molecular dipole moment distribution, and hydrogen bond populations, in comparison to experimental measurements. AbstractWe have applied an efficient electronic structure approach, the semiempirical self-consistent polarization neglect of diatomic differential overlap (SCP-NDDO) method, previously parametrized to reproduce properties of water clusters by Chang, Schenter, and Garrett [J. Chem. Phys. 128, 164111 (2008)], and now implemented in the CP2K package, to model ambient liquid water at 300 K (both the bulk and the liquid-vapor interface) and cubic ice at 15 K and 250 K. The SCP-NDDO potential retains its transferability and good performance across the full range of conditions encountered in the clusters and the bulk phases of water. In particular, we obtain good results for the density, radial distribution functions, enthalpy of vaporization, self-diffusion coefficient, molecular dipole moment distribution, and hydrogen-bond populations, in comparison to experimental measurements.2

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Section: Overview Of Scp-nddo Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Semiempirical Self-Consistent Polarization Description of Bulk Water, the Liquid−Vapor Interface, and Cubic Ice

et al. 2011

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“…1 This leads to a modified eigenvalue problem [Eq. (10)] that includes the Ewald pair potential: (20) The sum gives the Ewald field at the position of atom α, and must include terms due to both the QM-QM and QM-MM interactions. Since the MM charges are constant, the latter can be calculated only once outside the SCF, while the former is calculated using the current Mulliken charges at each SCF iteration in order to obtain, at the end of SCF procedure, a set QM charge distribution that is consistent with both the periodic MM field and the periodic QM field.…”

Section: Long-range Electrostaticsmentioning

confidence: 99%

Implementation of the SCC-DFTB Method for Hybrid QM/MM Simulations within the Amber Molecular Dynamics Package

et al. 2007

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Self-Consistent Charge Density Functional Tight Binding (SCC-DFTB) is a semi-empirical method based on Density Functional Theory, and has in many cases been shown to provide relative energies and geometries comparable in accuracy to full DFT or ab-initio MP2 calculations using large basis sets. This article shows an implementation of the SCC-DFTB method as part of the new QM/MM support in the AMBER 9 molecular dynamics program suite. Details of the implementation and examples of applications are shown.

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“…Owing to the large size of the ions, the initial survey calculations were performed by using the PM3 [30,31] semi-empirical algorithm, which was obtained as part of the Spartan '02 for Linux package (Wavefunction, Inc.). The starting points of the investigation were the protonated ions of compounds 1, 5 and 9 [3], to which we limited the calculations.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

Protonated nitro group as a gas-phase electrophile: Experimental and theoretical study of the cyclization of o-nitrodiphenyl ethers, amines, and sulfides

Moolayil

George

Srinivas

et al. 2007

J. Am. Soc. Mass Spectrom.

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A novel gas-phase electrophilic cyclization, initiated by the protonation of a nitro group, occurs for 2-nitrophenyl phenyl ether and for the analogous sulfide and amine, leading to heterocyclic intermediates in each case. Subsequently, the cyclic intermediates dissociate via two pathways: (1) unusual step-wise eliminations of two OH radicals to afford heterocyclic cations, [phenoxazine − H] + , [phenothiazine − H] + and [phenazine + H] + , and (2) expulsion of H 2 O, to yield a heterocyclic ketone, followed by loss of CO. The proposed structures of the gas-phase product ions and reaction mechanisms are supported by chemical substitution, deuterium labeling, accurate mass measurements at high mass resolving power, product-ion mass spectra obtained by tandem mass spectrometry, mass spectra of reference compounds, and molecular orbital calculations. Using a mass spectrometer as a reaction vessel, we demonstrate that, upon protonation, a nitro group becomes an electrophile and participates in cyclization reactions in the gas-phase.

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Optimization of parameters for semiempirical methods I. Method

Cited by 7,736 publications

References 18 publications

Semiempirical Self-Consistent Polarization Description of Bulk Water, the Liquid−Vapor Interface, and Cubic Ice

Semiempirical Self-Consistent Polarization Description of Bulk Water, the Liquid−Vapor Interface, and Cubic Ice

Implementation of the SCC-DFTB Method for Hybrid QM/MM Simulations within the Amber Molecular Dynamics Package

Protonated nitro group as a gas-phase electrophile: Experimental and theoretical study of the cyclization of o-nitrodiphenyl ethers, amines, and sulfides

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