Gasteiger charges (or Marsili-Gasteiger PEOE method) are empirical partial atomic charges calculated iteratively based on an atom's electronegativity, electron affinity, and ionization potential. They model charge distribution for molecular mechanics, docking, and chemoinformatics, providing a fast, non-quantum alternative to estimate molecular electrostatics.

AutoDock 4 (AD4) uses a specialized, semi-empirical force field that categorizes atoms by element and chemical environment (hybridization, h-bonding ability) to estimate binding free energy, including van der Waals, electrostatic, and hydrogen-bonding interactions. Key default types include aliphatic carbons (C), aromatic carbons (A), oxygens (OA), nitrogens (NA), and hydrogens (HD