[CPMD-list] Energy variations for calculations with torsional constraints

[Veronique Van Speybroeck]

Dear Salomon,

thanks for your constructive comments.  I will redo some of the 
calculations and comment later on to this list about the results..

Veronique

Salomon Billeter wrote:

>
>
>Hi Veronique,
>
>there have been a couple of small bug fixes in the constraints code
>recently, but this problem is quite possibly related to the choice of the
>geometry optimizer (default GDIIS/BFGS) which can be very efficient but
>also sometimes gets trapped far from a minimum. You can either restart the
>optimization from the last point, switch to the L-BFGS whose implementation
>is very careful in choosing the size of the trust radius and rejecting
>unsuccessful steps (keyword LBFGS; if you do that, choose also PRINT LSCAL
>ON to get some diagnostics about the progress of the optimization), or you
>can choose the conjugate gradient algorithm whose implementation performs a
>line search to get a good step size.
>Btw, do you want to do a periodic calculation? If not, ISOLATED MOLECULE
>alone is not sufficient, SYMMETRY should be set to zero instead of one to
>decouple the periodic images electrostatically from each other.
>
>Best regards,
>Salomon
>
>  
>

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Dr. ir. Van Speybroeck Veronique
Laboratorium voor Theoretische Fysica
Universiteit Gent
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email : veronique.vanspeybroeck at ugent.be
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