Another way to implement the Powell formula for updating Hessian matrices related to transition structures

A way to update the Hessian matrix according to the Powell formula is given. With this formula one does not need to store the full Hessian matrix at any iteration. A method to find transition structures, which is a combination of the quasi-Newton-Raphson augmented Hessian algorithm with the proposed Powell update scheme, is also given. The diagonalization of the augmented Hessian matrix is carried out by Lanczos-like methods. In this way, during all the optimization process, one avoids to store full matrices.