Charge Model 4 and Intramolecular Charge Polarization.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular modeling

Background:

• Partial atomic charges are crucial for modeling molecular charge polarization.
• The existing Charge Model 4 (CM4) offers accurate charge distributions with various density functionals and basis sets.

Purpose of the Study:

• To extend the applicability of CM4 to additional basis sets.
• To develop and present CM4M, a model optimized for the M06 suite of density functionals.
• To calculate and analyze gas-phase polarization effects using the developed charge models.

Main Methods:

• Extending Charge Model 4 (CM4) to six new basis sets.
• Developing Charge Model 4 for M06 (CM4M) optimized for ten basis sets within the M06 functional suite.
• Utilizing Löwdin or redistributed Löwdin population analyses of density functional electronic charge distributions to derive class IV partial atomic charges.
• Calculating CM4M/M06-2X/6-31G(d)//M06-2X/6-31+G(d,p) partial atomic charges for a set of organic molecules.

Main Results:

• Successful extension of CM4 to new basis sets.
• Development of CM4M, providing optimized partial atomic charges for M06 functionals.
• Demonstration of the models' ability to yield class IV partial atomic charges.
• Calculation of partial atomic charges for ethylene, CHnCl4-n, benzene, nitrobenzene, phenol, and fluoromethanol.

Conclusions:

• CM4 and CM4M provide reliable methods for calculating accurate partial atomic charges.
• The developed models are applicable across a range of density functionals and basis sets.
• The calculated charges can be used to study gas-phase polarization effects in molecules.