[QE-users] Question on Initial and final energies in NEB

[Stefano Baroni]

Dear M., I do not quite get what the problem is. The solution may just be a matter of definition. The “Minimum Energy Path” that the NEB is alleged to find is the path in configuration space which *connects two minima* (hence the answer to your question, I guess) and whose maximum energy (along the path) is minimum (with respect to other paths). Put in a different way. What are you using the NEB for? Finding an energy barrier, right? Between what? Stable molecular configurations, right? (hence energy minima).  Does this help? SB

> On 24 Aug 2018, at 13:12, Stella, Martina <martina.stella at kcl.ac.uk> wrote:
> 
> Hi,
>  
> I am new to NEBs calculations and I am getting familiar with the method. I have a couple of questions, maybe trivial, but for which I don't have an answer yet. Hopefully someone can help.  
> 
> 1) How is the energy for the Initial and final structure estimated when I keep the two configurations frozen? 
> 2)Should it be exactly the same as the final relaxed energies that I would get from completely separate calculations with the same simulation conditions and same geometries? 
> 3) If they are not expected to be exactly the same which factors does the difference I may see depend on? 
> 
> Thanks. 
> 
> 
> M. Stella
> Post-Doctoral researcher
> Physics Department, King's College London
> Strand,London WC2R 2LS UK
> 
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— 
Stefano Baroni -  SISSA, Trieste - http://stefano.baroni.me <http://stefano.baroni.me/>, stefanobaroni (Skype) 

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