[CP2K:4010] Energy conservation NVT/NVE simulation

[hut... at pci.uzh.ch]

Hi

the main problem is

     &QS
      EPS_DEFAULT 1.0E-12
      WF_INTERPOLATION PS
      EXTRAPOLATION_ORDER 3
    &END QS

change to WF_INTERPOLATION ASPC (the default) and maybe
increase the EXTRAPOLATION_ORDER slightly.
See 
J. Hutter, Car-Parrinello molecular dynamics
Wiley Interdisciplinary Reviews: Computational Molecular Science 2 (4) , pp. 604-612 
for an explanation.

You should also change to a more reasonable DFT functional.
LDA (PADE) will lead to an extremly overstructured system.
See 
J. Schmidt et al., 
Isobaric-isothermal molecular dynamics simulations utilizing density functional theory: An assessment of the structure and density of water at near-ambient conditions
Journal of Physical Chemistry B Volume 113, Issue 35, 3 September 2009, Pages 11959-11964

regards

Juerg

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich               E-mail:  hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----
To: cp... at googlegroups.com
From: "alber... at virgilio.it" 
Sent by: cp... at googlegroups.com
Date: 09/05/2012 09:44AM
Subject: [CP2K:4010] Energy conservation NVT/NVE simulation

Dear all,

I'm carrying out some tests to reproduce the VDOS of water and I used as
starting points the input files 'H2O-32.inp' and 'H2O-64.inp' in
tests/QS/benchmark directory.

In both cases I ran a NVT simulation at 300K for 15 ps followed by an NVE
simulation on the equilibrated system.

I'm puzzled about the results in the energies: in both NVT and NVE  the plot of
"Cons Qty" show a constant and linear drift while temperature, kinetic and
potential energy are equilibrated and stable.

Since "Cons Qty" should be conserved and this is not the case I think that
there are some problems in the setup of the simulation.
I did not modify the parameters of the benchmark inputs but I just added the
thermostat section in NVT and I modified only the printing option.

Thank you very much for your help and suggestions,

Alberto

  
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