Constrained Broyden Dimer Method with Bias Potential for Exploring Potential Energy Surface of Multistep Reaction Process.

To predict the chemical activity of new matter is an ultimate goal in chemistry. The identification of reaction pathways using modern quantum mechanics calculations, however, often requires a high demand in computational power and good chemical intuition on the reaction. Here, a new reaction path searching method is developed by combining our recently developed transition state (TS) location method, namely, the constrained Broyden dimer method, with a basin-filling method via bias potentials, which allows the system to walk out from the energy traps at a given reaction direction. In the new method, the reaction path searching starts from an initial state without the need for preguessing the TS-like or final state structure and can proceed iteratively to the final state by locating all related TSs and intermediates. In each elementary reaction step, a reaction direction, such as a bond breaking, needs to be specified, the information of which is refined and preserved as a normal mode through biased dimer rotation. The method is tested successfully on the Baker reaction system (50 elementary reactions) with good efficiency and stability and is also applied to the potential energy surface exploration of multistep reaction processes in the gas phase and on the surface. The new method can be applied for the computational screening of new catalytic materials with a minimum requirement of chemical intuition.