[QE-users] NEB with variable cell?

[A. Jain]

Hi Andrii,

I also have been playing around with the same issue on NEB. Here is the 
thread where I asked a similar question, perhaps it will help you: 
https://www.mail-archive.com/users@lists.quantum-espresso.org/msg36422.html

In my case I decided to average the cell parameters of the starting and 
final images and use that as my foundation to conduct neb. Since I was 
most interested in exploring the mechanism of photoisomerization which 
was concentrated around a particular set of atoms I don't believe it has 
posed a problem. So I guess my point is that the best course of action 
will simply depend on what you are intending to illustrate via neb.

At least that's my two cents, perhaps someone else has a better idea!

Apoorv
Cavendish Laboratory, University of Cambridge



On 2020-10-17 15:40, Andrii Shyichuk wrote:
> Dear Users,
> 
> I have two structures (A and B), on which I want to do a NEB
> calculation, using them as the initial and the final images.
> 
> The problem is: they differ in their cell size by about 1%.
> 
> My options:
> 
> 1. Do NEB with lattice vectors from structure A, then another NEB with
> vectors from structure B, and then another one with the average
> vectors. That, obviously, would be an approximation, and I will see
> how bad it is from the results.
> 
> 2. Do manual frozen "NEB", where I simply interpolate structure A into
> structure B in N steps and just do SCFs. Not a NEB per se, but that's
> something.
> 
> 3. Interpolate A cell vectors into B cell vectors in N steps, and do
> atomic position relaxations at each set of vectors. Not sure if the
> moving atoms will move the way I expect them to move.
> 
> 4. Get the reaction path from option 1, and then do vc-relax at each
> step, freezing the moving atoms at the path. However, constraints in
> PW do not work with vc-relax, as I can see from the manual. Thus, what
> I can do is option 3 with constraints.
> 
> So, what would you do? What do people usually do in situations like 
> this?
> 
> Thank you in advance.
> Best regards.
> Andrii Shyichuk
> Faculty of Chemistry, University of Wrocław, Poland.
> 
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