[CPMD-list] how to do constraint optimization?

[Ari P Seitsonen]

Dear Lan-Feng,

   In addition to Axel's recommendations I could maybe add that if the 
constraints that you want to fulfill are not very close to the wanted 
values in the optimised geometry you can use RESTRAINTS to bias the system 
to approach the wanted values. This option (please check the manual for 
the syntax and usage; it's almost identical to the case of CONSTRAINTS) 
adds a harmonic potential around the restrained value, and by increasing 
the force constant you can force your system closer and closer to the 
wanted value. This option, however, should only be used to approach a 
configuration since it doesn't lead to conserved dynamics (like the 
CONSTRAINTS do).

     Greetings from Garching bei Munich / Bavaria,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   CNRS & IMPMC, Université Pierre et Marie Curie
       4 place Jussieu, case 115 / F-75252 Paris
   Tel: +33-1-4427 7542, Fax: +33-1-4427 3785, GSM: +33-6-6736 3820

On Tue, 6 Dec 2005, Lan-Feng Yuan (lyuan at Princeton.EDU) wrote:

>  Dear CPMD users,
>
>  I want to optimize a structure under a constraint, e.g., the distance between atoms 1 and 2 must be 3 A. According to manual, the way is to add CONSTRAINTS ... END CONSTRAINTS in &ATOMS. Emm ... but how about the initial geometry? It seems that I don't need to make the input geometry satisfy the constraint, because in the output it prints the current value and its difference with the desired value. However, the program updates the structure by thousands of times, but never gets convergence. And the constraint is not reached neither. What's the algorithm to do constraint optimization? Is this feature kind of broken, or do I miss something? Thank you very much!
>
>  Lan-Feng
>
> ----------------------------
> Dr. Lan-Feng Yuan,
> Postdoctoral Associate,
> Department of Chemistry,
> Princeton University,
> Princeton, NJ 08544, USA
> Office Phone: 1-609-258-1834
> Fax: 1-609-258-6746
> ----------------------------
> _______________________________________________
> CPMD-list mailing list
> CPMD-list at cpmd.org
> http://cpmd.org/mailman/listinfo/cpmd-list
>