First-principle molecular dynamic simulations along the intrinsic reactionpaths

Presented is an algorithm for performing the ab initio molecular dynamic (M D) simulations along the predetermined intrinsic reaction paths (TRP). The proposed approach has been implemented within the projector augmented-wave DFT methodology (PAW program). The slow-growth MD simulations along the IRP has been applied for the reactions of (i) the HCN --> CNH isomerization re action, (ii) the conrotatory ring opening of cyclobutene, (iii) the prototy pe SN2 reaction Cl- + (CHCl)-Cl-3 --> ClCH3 + Cl-, and (iv) the chloroprope ne isomerization Cl-CH2-CH=CH2 = CH2=CH-CH2Cl. The results show that the sl ow-growth MD approach along the predetermined IRP leads to smooth free-ener gy profiles; use of a well-defined reaction coordinate (RC) reduces the pro blem of the free-energy hysteresis, Thus, the slow-growth simulations along the IRP typically require less time steps than the standard approach with an a priori chosen RC. The illustrative examples show that the applied meth odology works well for the reactions involving concerted changes in many ge ometrical variables as well as in the cases when the finite-temperature pat hs strongly deviate from the IRP.