[DFTB-Plus-User] Correct Way to Run MPI-enabled DFTB+ (Conda Installation)

[Ankur Gupta]

Dear Dr. Aradi,

Yes, I am also not able to understand what the source of this noise is. I
am playing around with various options for the FIRE optimizer, but so far,
I haven't succeeded in optimizing the structure within a reasonable number
of steps.

I have attached a sample input file with the email. I would be highly
grateful if you could provide any further insight into the given
structure's optimization.

Best,
Ankur

On Mon, May 2, 2022 at 7:32 AM Bálint Aradi <aradi at uni-bremen.de> wrote:

> Dear Ankur,
>
> For sure, the xTB parameters were created without considering periodic
> structures. But even with a suboptimal parametrization, I'd not expect
> problems with the lattice optimization convergence. This looks to me
> more like some noise, which makes optimization with tight tolerances
> problematic. But currently, I am somewhat puzzled, where this noise
> should come from...
>
> Best regards,
>
> Bálint
>
>
> On 29.04.22 21:03, Ankur Gupta wrote:
> > Dear Dr. Aradi,
> >
> > I am already using the new geometry optimizers. I have tried all three
> > optimizers available (Rational, LBFGS, FIRE). It seems like the
> > optimization starts wandering when the max. gradient reaches around
> > 1.00E-03. So, we probably need to decrease the step size when the
> > maximum gradient is around that value. I am currently working with
> > simple periodic organic molecules, with only two molecules in a unit
> > cell, so I expect the optimization to converge within 150 steps.
> >
> > I have used GFN2-xTB (in the xTB code) for molecular optimizations of
> > large molecules and found it to be quite robust for a wide variety of
> > cases. However, since the xTB methods have not been parameterized for
> > periodic systems, I was wondering if that's the reason for their poor
> > performance in optimizing periodic systems.
> >
> > Best,
> > Ankur
> >
> > On Fri, Apr 29, 2022 at 2:36 AM Bálint Aradi <aradi at uni-bremen.de
> > <mailto:aradi at uni-bremen.de>> wrote:
> >
> >     Dear Ankur,
> >
> >      > I have another question related to the usage of DFTB+. I am
> >     currently
> >      > trying to optimize periodic organic systems (containing around
> >     60-110
> >      > atoms) using the GFN2-xTB method; however, it seems like the
> >     geometry
> >      > optimization is extremely slow in terms of gradient convergence.
> For
> >      > example, in around 300 geometry optimization steps, the gradient
> >     norm
> >      > dropped from 0.72 H/a0 to only 0.0005499 H/a0. Is there a way to
> >     speed
> >      > up the gradient convergence so that the geometry optimization
> >     finishes
> >      > in fewer steps?
> >
> >     Use the new geometry optimizers (Driver = GeometryOptimization {}).
> >     Depending on the system, if the potential surface is very flat, it
> can
> >     be difficult to obtain the minimum.
> >
> >     Best regards,
> >
> >     Bálint
> >
> >     --
> >     Dr. Bálint Aradi
> >     Bremen Center for Computational Materials Science, University of
> Bremen
> >     http://www.bccms.uni-bremen.de/cms/people/b-aradi/
> >     <http://www.bccms.uni-bremen.de/cms/people/b-aradi/>
> >
> >     _______________________________________________
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> >
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> >
> >
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>
>
> --
> Dr. Bálint Aradi
> Bremen Center for Computational Materials Science, University of Bremen
> http://www.bccms.uni-bremen.de/cms/people/b-aradi/
>
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