[CP2K:2608] Weird forces

[Laino Teodoro]

Dera Kyle,

this is what I get with today executable:

  ENERGY| Total FORCE_EVAL ( QMMM ) energy (a.u.):             
-17.167829467231705

        6
  FORCES| (a.u.)
   O        -0.0273600235        0.0000000005       -0.0192905160
   H         0.0055371466        0.0000000000        0.0300429372
   H         0.0252415319        0.0000000000       -0.0056232711
   O        -0.0109789207       -0.0000000000       -0.0187157708
   H        -0.0232318214        0.0000000000        0.0038225897
   H         0.0307346317        0.0000000000        0.0099562863


Please check your compilation/installation.
Best Regards,
Teo

On 2 Mar 2010, at 20:27, Kyle wrote:

> Dear experts,
>
> I'm a new user of cp2k and I'm trying to learn to use it starting from
> regtests.  When I modified a regtest and printed out the forces, they
> look weird to me.
> The system has 2 water molecules:  1 QM and 1 MM.  These two molecules
> are on the same plane (y coordinates are 0).  I've turned off
> periodicity so that there shouldn't be any forces on y direction, but
> in the output, I see forces like this:
>
>        6
>  FORCES| (a.u.)
>   O         2.3480705473       -0.1758649026       -0.8433977677
>   H         0.0546465145        0.2126359382       -0.2627404736
>   H        -2.3771471785       -0.0367742437        1.1356514635
>   O         0.0034510142       -0.0004321212        0.0104995913
>   H        -0.0506123656        0.0004871507       -0.0429205567
>   H         0.0215013774        0.0001120302        0.0032855353
>
> Is it wrong?  I've tried exactly the same calculation using an early
> executable (from 2008) and got this:
>
>        6
>  FORCES| (a.u.)
>   O        -0.0273598561        0.0000000005       -0.0192903618
>   H         0.0055371483        0.0000000000        0.0300428993
>   H         0.0252415166        0.0000000000       -0.0056232623
>   O        -0.0109790737        0.0000000000       -0.0187158940
>   H        -0.0232318220        0.0000000000        0.0038225881
>   H         0.0307346315        0.0000000000        0.0099562861
>
> These forces make much more sense to me, but why is there
> inconsistency between the two versions? I've uploaded input files in
> 2H2O.tgz.
>
> Thanks a lot in advance,
>
> Yours,
> Kyle
>
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