Running OPTIM

Any number of optimisation 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 $10^{-5}$ and the RMS force is also less than $10^{-5}$. 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 §4.