If it is not near to the transition state, identify geometries on both sides of the transition state (these will be separated in the output by the message 'REACTANTS AND PRODUCTS SWAPPED AROUND'), and use these to start a new SADDLE calculation. less than 0.2), refine the geometry using TS. Options at this point are: If it is near to the transition state (the gradient norm has been dropping for reactants or products, or the 'DISTANCE A-B' is small, e.g. In a SADDLE calculation, both reactants and products are on the same side of the transition state. In a FORCE calculation, the mass of an atom is zero. AT LEAST ONE ATOM HAS A ZERO MASS (FATAL) This sometimes happens naturally, particularly with exotic systems.

This is often caused by faulty data, so the data should be checked to see if anything is wrong. The default SCF convergers have not worked. Check the dependent atom numbers in the symmetry data. A SYMMETRY FUNCTION IS USED TO DEFINE A NON-EXISTENT ATOM (FATAL) S ymmetry functions can only be used in the definition of atoms or dummy atoms. The smallest system that can have vibrations is a diatomic molecule. A SINGLE ATOM HAS NO VIBRATIONAL MODES (FATAL)Īn attempt has been made to calculate the vibrations of a single atom. The pair of options, 1SCF with a path calculation, is not allowed, except in a RESTART calculation. The following alphabetical list gives more complete definitions of the messages printed. However, when an error occurs it is useful to have more information than is given in the standard messages. MOPAC produces several hundred messages, all of which are intended to be self-explanatory.

Error messages produced by MOPAC Error messages produced by MOPAC

Zmatrix reference atoms