NEB-IRC activation energy pipeline

Overview

Computes a reaction activation energy end to end — optimize reactant and product, find the minimum energy path with climbing-image NEB, refine the transition state with a Hessian, and confirm it with IRC — using GFN2-xTB through pysisyphus. Outputs a verified TS geometry, the barrier (ΔE‡; ΔG‡ after thermal corrections), an IRC energy profile (irc_energy_profile.png), and an animated TS imaginary-mode viewer (ts_imaginary_mode.html). Verification is required, not optional: a converged TS is meaningless until its single imaginary mode and IRC endpoints are checked.

When to Use

• Finding the transition state for an elementary reaction step and its activation energy
• Computing a reaction barrier (ΔE‡ or ΔG‡) to rank a series of related reactions
• Running a climbing-image NEB / minimum energy path between a reactant and product
• Verifying a candidate TS with IRC — does it connect the intended reactant and product?
• Screening barriers at a cheap semi-empirical level before committing DFT time