[DFTB-Plus-User] DFTB+ Geometry Relaxation external socket

[James A Charles]

Hi,


Thank you very much for the response. I have tried the LBFGS and indeed that is the one I have had the most luck with. However, It still takes around a 1000 iterations and I was hoping that I could reduce that number. With the LBFGS algorithm, do you know how important the initial guess is? Is the final result dependent on the initial guess?


I have also tried larger systems with a solute embedded in the solvent and that is much more difficult to converge. I apply what I think is the standard procedure for geometry relaxation of first relaxing internal coordinates keeping the lattice vectors constant and then allowing cell relaxation.


Thanks,

James

________________________________
From: DFTB-Plus-User <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> on behalf of Ben Hourahine <benjamin.hourahine at strath.ac.uk>
Sent: Tuesday, April 24, 2018 3:44:00 AM
To: dftb-plus-user at mailman.zfn.uni-bremen.de
Subject: Re: [DFTB-Plus-User] DFTB+ Geometry Relaxation external socket


Hello James,


apologies about the delay in replying. The socket interface is for use with the external I-Pi code (https://github.com/i-pi/i-pi), which can relax geometries, but is better known for advanced molecular dynamics (various forms of path integral, replica exchange, ...). They provide a few example scripts for DFTB+ (both the dftb_in.hsd and their own input.xml files). We are currently working on a section for the recipes document that shows this in use.


DFTB+ can also be used via the ASE software (https://wiki.fysik.dtu.dk/ase/), which doesn't use the socket interface, but instead via disc files.


For the geometry drivers built into DFTB+, did you get a chance to try the LBFGS optimiser as this might be better for your case?


Regards


Ben

On 17/04/18 02:24, James A Charles wrote:

Hello,


I have been trying to relax ice crystals with DFTB+ and have tried the drivers included in DFTB+ without much luck. I was reading through the documentation and noticed Socket{} as a driver. What is the purpose of this? and is there an example of which external tools this works with?


Thanks,

James



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      Dr. B. Hourahine, SUPA, Department of Physics,
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