Fast, efficient generation of high-quality atomic charges. AM1-BCC model: II. Parameterization and validation

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Quantum Chemistry

Background:

• Accurate atomic charges are crucial for molecular simulations.
• Existing methods for generating charges can be computationally expensive or less accurate.
• The need for efficient and reliable charge models for organic molecules in polar media is significant.

Purpose of the Study:

• To present the first global parameterization and validation of the novel AM1-BCC charge model.
• To develop a method that efficiently generates high-quality atomic charges for computer simulations.
• To create atomic charges that emulate the high-level ab initio electrostatic potential (ESP).

Main Methods:

• Developed the AM1-BCC charge model, combining AM1 population charges with bond charge corrections (BCCs).
• Parameterized BCCs by fitting to the HF/6-31G* ESP of over 2700 diverse organic molecules.
• Validated the model using hydrogen-bonded dimer energies and relative free energies of solvation with the AMBER force field.

Main Results:

• AM1-BCC accurately reproduces hydrogen-bonded dimer energies (0.95 kcal/mol RMSD) and DNA dimer energies (0.9 kcal/mol RMSD).
• Calculated relative free energies of solvation show excellent agreement with experimental values (0.69 kcal/mol).
• The AMBER force field with AM1-BCC charges maintained a correlation coefficient above 0.96 in all validation tests.

Conclusions:

• AM1-BCC provides a fast, accurate, and robust method for generating atomic charges for organic molecules.
• It serves as a viable alternative to computationally intensive HF/6-31G* ESP-fit charges.
• The presented parameters are suitable for general use with the AMBER force field in molecular simulations.