Using bonding to guide transition state optimization

Optimization of a transition state typically requires both a good initial guess of the molecular structure and one or more computationally demanding Hessian calculations to converge reliably. Often, the transition state being optimized corresponds to the barrier in a chemical reaction where bonds are being broken and formed. Utilizing the geometries and bonding information for reactants and products, an algorithm is outlined to reliably interpolate an initial guess for the transition state geometry. Additionally, the change in bonding is also used to increase the reliability of transition state optimizations that utilize approximate and updated Hessian information. These methods are described and compared against standard transition state optimization methods.