Efficient Chain-of-States Approach for Locating Transition State via Spherical Optimization

The Chain-of-states(CoS) methods like nudge elastic band(NEB) method can be used to determine the minimum energy path (MEP) and transition state (TS) between two end local minima. However, the CoS methods are inefficient for difficult cases where the two ends are far apart with chemically insignificant part(s) in the MEP. We present here a method based on spherical optimization (SOPT), in which the SOPT method generates model end structures for CoS methods under the constraint of constant root-mean-square distance (RMSD) between two ends that is chosen to cover only the chemically significant part. We demonstrate the robustness and efficiency of our method with two examples, the CHOH dissociation channel and the first step of Aldol reaction. In both cases, the SOPT-based NEB calculations always reach the convergence to the correct MEPs with much less computational cost, whereas the regular NEB calculations fail under certain setups.