A revised TS-BFGS update formula

Abstract A modification of the TS-BFGS Hessian update formula for optimizing transition state structures is presented. This modification involves the introduction of a term which accounts for the mismatch in the units of the original formula. This revised update was tested on a variety of transition state structures and compared to the minimization of sum of squares method by Powell (VA) as well as the Murtagh–Sargent–Powell (MSP) Hessian update formula. The update presented performed as well as the MSP update for the structures tested and was much more efficient (in terms of the number of function evaluations required for convergence) than VA. Thus (revised) TS-BFGS is believed to be a viable method for transition state optimization.