AIDER

AIDER allows MOPAC to optimize an ab initio geometry. To use it, calculate the ab initio gradients using, e.g., Gaussian [14]. Supply MOPAC with these gradients, after converting them into kcal/mol. The geometry resulting from a MOPAC run will be nearer to the optimized ab initio geometry than if a single step were taken using the geometry optimizer in Gaussian.