Running OPTIM

Any number of optimization steps can be run with a single call to OPTIM, as specified by the keyword STEPS. When the derivatives are provided by an external program the default value NSTEPS=1 will generally be needed. The default convergence criteria for eigenvector-following and steepest-descent runs are that the maximum unscaled step size for any coordinate (or eigenvector, depending upon the scaling criterion) is less than 0.002 and the RMS force is less than 10^-5. Alternatively, the program will also detect convergence if the RMS force is less than 10^-6 and the maximum unscaled step is less than 0.1. The number of negative Hessian eigenvalues must also agree with the search type requested. These convergence criteria can be overruled by the CONVERGE keyword, as described in §II.