CI-NEB with/without OPTIMIZE_END_POINTS

[Abhishek Bagusetty]

Hi All,

I have performed a TS search using CI-NEB method and this is the procedure, 
I have adopted. 

1. The Reactant (Image initial) and Product (Image final) are relaxed with 
geometry optimization.
2. Images (image1.png in the attachment) between the initial and final 
images are chosen and CI-NEB is performed with these parameters :


   - ROTATE_FRAMES F
   - ALIGN_FRAMES F
   - OPTIMIZE_END_POINTS F


This is the energy profile that is obtained and as it is clearly seen that 
the reactants and products are no longer at the minima. I have tried this 
with 10,12 and 16 images.
But in all the cases the images that are next to the reactant (first) and 
product (last) reach minimum. 

This (image2.png in the attachement) is the energy profile that is obtained 
with using the same images as above but with OPTIMIZE_END_POINTS as TRUE. 
The reactants and products are relaxed using geometry optimization for this 
case as well.
This plot makes sense as the reactants and products are at minima with 
respect to other images. 

   - ROTATE_FRAMES F
   - ALIGN_FRAMES F
   - OPTIMIZE_END_POINTS T


Can someone please explain what could have been going on with and without 
using the OPTIMIZE_END_POINTS and which one show be considered ?

Thanks,
Abhishek


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Abhishek Bagusetty
PhD Student, Computational Modeling & Simulation
Center for Simulation and Modeling
Department of Chemical & Petroleum Engineering
University of Pittsburgh
Pittsburgh, PA - 15261
Office : 920 Benedum Hall
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