Electrostatic potential fitted charges

St.-Amant, A., W. D. Cornell, P. Kollman, and T. A. Halgren. 1995. Calculation of Molecular Geometries, Relative Conformation Energies, Dipole Moments, and Molecular Electrostatic Potential Fitted Charges of Small Organic Molecules of Biochemical Interest by Density Functional Theory. J. Comp. Chem. 16, 1483. 

St.-Amant A, Cornell WD, Kollman PA, Halgren TA (1995) Calculation of molecular geometries, relative conformational energies, dipole-moments, and molecular electrostatic potential fitted charges of small organic-molecules of biochemical interest by density-functional theory, J Comput Chem, 16 1483-1506... 

Despite these fairly accurate dipole moments, DFT molecular electrostatic potential fitted charges are most likely not appropriate for simple additive molecular mechanical force fields. For these types of force fields to be accurate in aqueous environments, a priori polarization of molecules is required. The DFT charges are too gas phase-like, and initial tests indicate that the charges are too small and their electrostatic interactions with prepolarized water molecules (such as the SPC, TIP3P, and TIP4P water models ) are too weak. On a brighter note, as nonadditive, polarizable, force fields become more popular, the ability to accurately reproduce gas phase dipole moments will be extremely desirable. 

Calculation of Molecular Geometries, Relative Conformational Energies, Dipole Moments, and Molecular Electrostatic Potential Fitted Charges of Small Organic Molecules of Biochemical Interest by Density Functional Theory. 

Molecular properties can be calculated at any given geometry, including electrostatic multipole moments up to hexadecapoles polarizabilities and hyperpolarizabilities electrostatic potential fitted charges Mulliken population electron density vibrational spectrum and thermochemical properties. 

Jaguar s solvation module uses a self-consistent reaction field (SCRF) model, which couples an accurate ab initio description of the charge distribution to a well-defined and realistic representation of the molecular cavity. The SCRF calculation is done by first calculating the gas phase wavefunction of the solute molecule, from which the electrostatic potential fitted charges are passed to an efficient finite element solver, which determines the reaction field by numerical solution of the Poisson-Boltzmann equations and represents the solvent as a layer of charges at the solute s molecular surface, which serves as the dielectric continuum boundary. The solvent point charges are incorporated in a subsequent wavefunction evaluation and the process is repeated until self-consistency is obtained. The cost is roughly twice that of a gas phase calculation. 

Electrostatic potential-derived charges assign point charges to fit the computed electrostatic potential at a number of points on or near the van der Waals surface. This sort of analysis is commonly used to create input charges for molecular mechanics calculation. 

Tab. 1.3 Comparison between different sets of atomic point charges for a zwitterionic Gly-Ala dipeptide in aqueous solution. D-RESP electrostatic potential derived charges [12] fitted to all 36 configurations. Hirshfeld average value of the Hirshfeld charges [89c] along the full trajectory, Amber AMBER 1995 force field [86], Gromos GROMOS96 force field [85], The charges of equivalent atoms are imposed to be equal.

T. R. Stouch and D. E. Williams, /. Comput. Chem., 14, 858 (1993). Conformational Dependence of Electrostatic Potential-Derived Charges Studies of the Fitting Procedure. 

Electrostatic potential-derived charges While net atomic charges q are not rigorously defined quantum mechanical properties they can be derived by fitting the classical electrostatic potential due to the charges q to the rigorously defined quantum mechanical electrostatic potential. 

This study obviously gave very satisfactory agreement with the experimental data. However, a subsequent calculation by Merz and Kollman showed that the results were very sensitive to the charge model used for the inhibitor [Merz and Kollman 1989]. The charges for the inhibitor were obtained by electrostatic potential fitting in each case, though with... 

Table I. Comparison of the partial charges on the individual atoms of H2O and CO2. Mulliken charges as well as the charges derived by fitting the electrostatic potentials (CHELPG charges) in electrons (e).

Berente, I., Czinki, E., and Naray-szab6, G. (2007). A combined electronegativity equalization and electrostatic potential fit method for the determination of atomic point charges. Journal of Computational Chemistry 28,12, pp. 1936-1942. 

Slouch, T. R., and Williams, D. E. (1993]. Conformational dependence of electrostatic potential-derived charges Studies ofthe fitting procedure, fournai of Computationai Chemistry 14, 7, pp. 858-866. 

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