If you don't have animation click the image to see an alternate display. The measurement tool displays bond lengths, bond angles, torsion dihedral angles or interatomic distances. An example of a ChemPen3D style reaction constructed with geometry-optimized molecules appears to the left. The Reaction Tool, below, is used to balance the reaction and set its conditions. While certainly no substitute for calorimetry, ChemPen3D can usually predict whether a reaction will be endothermic or exothermic, spontaneous or non spontaneous.
Calculations are atomistic, classical and semi empirical.
These force fields are optimized for specific classes of molecules. ChemPen3D can handle metal complexes. Allinger, N. L. J. Am. Despite it power and features ChemPen3D is a small program with small system requirements. The minimum recommended system is a 33MHz 486DX, Windows 95,98, or NT 16MB RAM and 2MB free HDD space.