Charge distributions and chemical effects. XLII. Atomic charges and their role in energy calculations

1986 ◽  
Vol 29 (3) ◽  
pp. 305-310 ◽  
Author(s):  
S. Fliszár
Keyword(s):  
Atomic Charges ◽  
Energy Calculations ◽  
Charge Distributions ◽  
Chemical Effects

Charge distributions and Chemical effects. XII. A unifying concept

1976 ◽  
Vol 54 (18) ◽  
pp. 2839-2846 ◽  
Author(s):  
Sándor Fliszár
Keyword(s):  
Positive Charge ◽  
Recent Literature ◽  
Atomic Charges ◽  
Charge Distributions ◽  
Chemical Effects ◽  
Carbonium Ions ◽  
Inductive Effects ◽  
Definition Of ◽  
C Nmr

Major inconsistencies which are currently acknowledged in discussions involving atomic charges, inductive effects, 13C nmr shifts, and stability of carbonium ions are removed (i) by the use of an appropriate definition of charges and (ii) by the recognition that in alkanes and alkyl carbonium ions any decrease in positive charge at carbon atoms results in a downfield 13C shift. Methyl appears to be less electron withdrawing than hydrogen, and stability of carbonium ions is associated with dispersion of positive charge at the carbonium center, in line with the more traditional views which are repeatedly challenged in recent literature.

SAMPL6 Octanol-Water Partition Coefficients from Alchemical Free Energy Calculations with MBIS Atomic Charges

2019 ◽  
Author(s):  
Maximiliano Riquelme ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Free Energy ◽  
Electron Density ◽  
Free Energy Calculations ◽  
Basis Set ◽  
Energetic Cost ◽  
Atomic Charges ◽  
Free Energies ◽  
Energy Calculations ◽  
Alchemical Free Energy ◽  
Alchemical Free Energy Calculations

In molecular modeling the description of the interactions between molecules forms the basis for a correct prediction of macroscopic observables. Here, we derive atomic charges from the implicitly polarized electron density of eleven molecules in the SAMPL6 challenge using the Hirshfeld-I and Minimal Basis Set Iterative Stockholder(MBIS) partitioning method. These atomic charges combined with other parameters in the GAFF force field and different water/octanol models were then used in alchemical free energy calculations to obtain hydration and solvation free energies, which after correction for the polarization cost, result in the blind prediction of the partition coefficient. From the tested partitioning methods and water models the S-MBIS atomic charges with the TIP3P water model presented the smallest deviation from the experiment. Conformational dependence of the free energies and the energetic cost associated with the polarization of the electron density are discussed.

Charge distributions and chemical effects

1980 ◽  
Vol 68 ◽  
pp. 227-234 ◽  
Author(s):  
A.E. Foti ◽  
V.H. Smith ◽  
S. Fliszár
Keyword(s):  
Charge Distributions ◽  
Chemical Effects
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