[CPMD-list] Energy components in PIMD

[Axel Kohlmeyer]

On Fri, 30 May 2008, ukasz Walewski wrote:

LW> Applying a thermostat on the electrons gave the stable fictitious
LW> dynamics, however the conserved energy took over the drift... (see
LW> attached graphs and the input file). Rate of the drift is ~1e-6 Ha/ps,
LW> i.e. smaller by the factor of 10 than the drift in EKINC without a
LW> termostat. My feeling is that it is better to have the total energy
LW> conserved and live with the drift in EKINC. What do you think ?

i would go for the thermostat. it is safer.

LW> I turned the restraints on. Following the route you outlined in the
LW> previous e-mail I came upon the kval = 0.000001 [unknown units] which
LW> gives the force of 1.8e-6 [a.u.] in the 1 A distance from the
LW> equilibrium position. The forces usually seen during MD run are of the
LW> order of 1e-3 - 1e-4 while in-plane forces are 1e-5. Isn't it possible
LW> that the drift in EHAM comes from the restraints ?

no. at least it should not. there were some funnies in the code related
to restraints that we fixed recently, but if i remember correctly those
were limited to BO dynamics. it is, however, extremely simple to verify
it. just run the exact same trajectory without the restraints.

cheers,
   axel.

LW> 
LW> Regards,
LW> Lukasz
LW> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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