[CP2K:3682] Are OT vs. non-OT simulations comparable

hut... at pci.uzh.ch hut... at pci.uzh.ch
Fri Dec 23 14:46:31 CET 2011


Hi

the final energy will not depend (up to some numerics) on the
optimizer used, as long as you are using the same electronic
structure method.
In your example, however, you are changing the method by requesting
"smearing". In this case the total energies will be different
(but can be similar if the band gap is very large).

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: cp2k <cp... at googlegroups.com>
From: Joseph Han 
Sent by: cp... at googlegroups.com
Date: 12/23/2011 12:10AM
Subject: [CP2K:3682] Are OT vs. non-OT simulations comparable

I'm a new user to cp2k, and was curious about the OT versus non-OT
simulation results.  Specifically, assuming that the number and types
of atoms in two simulations are the same, are the energies directly
comparable in an OT versus non-OT simulation.

More specifically, suppose that I am looking at different crystal
structures of the same stoichiometry.  In one cell configuration, I
need to use

      &OT ON
        MINIMIZER CG
        LINESEARCH 3PNT
        PRECONDITIONER FULL_ALL
      &END OT

to achieve convergence.  For the other configuration, I used

      ADDED_MOS 30
      &SMEAR  ON
         METHOD FERMI_DIRAC
         ELECTRONIC_TEMPERATURE [K] 600
      &END SMEAR
      &DIAGONALIZATION
         ALGORITHM STANDARD
      &END DIAGONALIZATION
      &MIXING
         METHOD BROYDEN_MIXING
         ALPHA   0.1
         BETA    1.5
         NBROYDEN  8
      &END

Can the total energies be compared when using different SCF
convergence techniques?  Does changing ADDED_MOS affect the ability to
compare results (i.e. does it represent a change in basis set)?

Thanks

Joseph

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