 Its selection mechanism enables to specify parts of a molecule by simple expressions (SMILES, SMARTS, element types).This selection can be used by all modeling classes like the processors or force fields.Fast and stable implementations of the popular force fields CHARMM, Amber, and MMFF94 can be combined with BALL's minimizer and simulation classes (steepest descent, conjugate gradient, L-BFGS, and shifted L-VMM).