Molcas Forum

liurui

Member

Registered: 2024-04-18

Posts: 7

Question about tracing reaction pathways through MECIs in OpenMolcas

Hello everybody,
We would like to seek your advice on how to correctly obtain reactants and products that correspond to different Sm and Sn states through MECI points calculated using OpenMolcas.

We have identified two MECI points in our system: one between S₀ and S₁ (MECI₁), and another between S₁ and S₂ (MECI₂). To explore the reaction pathways, we have used Gaussian’s downhill-following method (with input files similar to the example below) to trace possible products from these MECIs, and we have successfully obtained reasonable structures.

However, we are not sure how to determine which of these downhill optimizations truly correspond to the intended reaction pathways starting from the respective MECIs. Is it generally acceptable to optimize the reactants and products directly, or would you recommend using a linear interpolation in internal coordinates (LIIC) to connect them and verify the reaction path?

Previously, we anticipated the existence of these MECI/MECP points because we had performed calculations with Gaussian using the guess=mix keyword to intentionally break symmetry, which did suggest state crossings. But we are still uncertain whether the crossing points we obtained actually correspond to the correct electronic states.

We would be very grateful for any guidance or suggestions on how to validate these pathways and ensure that the downhill paths indeed match the expected states and reaction channels.