[CP2K:6557] Checking for a True Minima

[Jörg Saßmannshausen]

Hi Olivia,

further what Matt and Ian said, there is also the restart option which will 
take care of getting the right coordinated, i.e. the converged ones:

@IF 1
&EXT_RESTART ON
  RESTART_DEFAULT F
  RESTART_FILE_NAME FILENAME.restart 
  RESTART_POS T
  RESTART_COUNTERS T
  RESTART_VEL T
  RESTART_THERMOSTAT T
&END EXT_RESTART
@ENDIF

This is also very useful if you need to restart a geometry run. Please note: 
in this case you will need to increase the number of steps as you are 
restarting the counters.

I hope that helps a bit.

All the best from a sunny London

Jörg


On Thursday 28 May 2015 09:14:23 Iain Bethune wrote:
> Hi Olivia,
> 
> Yes, once you have the optimised structure, you can take the same input
> file, set RUN_TYPE to VIBRATIONAL_ANALYSIS and add a &VIBRATIONAL_ANALYSIS
> section.  You may remove the &MOTION section if you like, but I think CP2K
> will ignore it in any case.
> 
> You need to make sure that you start from the optimised geometry (including
> cell), so you either need to edit the coords into your input file, or read
> from a file (see SUBSYS/TOPOLOGY/COORD_FILE_NAME and
> SUBSYS/CELL/CELL_FILE_NAME).  Assuming you are doing DFT, it will also be
> much quicker if you start the SCF optimisation for each of the
> single-point calculations required by the vibrational analysis
> finite-difference scheme from the optimised wavefunctions you obtained at
> the end of your CELL_OPT.  This can be done via the
> FORCE_EVAL/DFT/SCF/SCF_GUESS keyword set to RESTART.
> 
> There are example inputs in the directory e.g.
> cp2k/tests/QS/regtest-gpw-2-1/H2-vib.inp that may help.  There are also
> some discussions about the different options that can be used in
> VIBRATIONAL_ANALYSIS in older posts to this group that may also be
> helpful.
> 
> Cheers
> 
> - Iain
> 
> --
> 
> Iain Bethune
> Project Manager, EPCC
> 
> Email: ibet... at epcc.ed.ac.uk
> Twitter: @IainBethune
> Web: http://www2.epcc.ed.ac.uk/~ibethune
> Tel/Fax: +44 (0)131 650 5201/6555
> Mob: +44 (0)7598317015
> Addr: 2404 JCMB, The King's Buildings, Peter Guthrie Tait Road, Edinburgh,
> EH9 3FD
> 
> > On 27 May 2015, at 17:15, Olivia Lynes <livl... at gmail.com> wrote:
> > 
> > Hi all,
> > 
> > I'm a new user of CP2K and have started off doing direct cell
> > optimisations on  32/64/128 water boxes. The aim is to introduce small
> > atoms into the water boxes and look at the behaviour.
> > 
> > All of the cell optimisations have completed, is there a way to check
> > that the optimised geometry has reached a true minima not a maxima?
> > 
> > Previously I would do a vibrational frequency analysis which gave the
> > vibrational frequencies and infra-red spectra and if imaginary
> > frequencies were found distort the geometry along the imaginary
> > frequency and then re-optimise the structure. .
> > 
> > Is there something similar I can do using CP2K?
> > 
> > Is it just a case of once the cell optimisation is complete altering the
> > input file so RUN_TYPE is VIBRATIONAL_ANALYSIS and including a
> > VIBRATIONAL_ANALYSIS section? I'm a bit unsure of what the input section
> > for this type of job should look like, would I need to remove the
> > CELL_OPT section?
> > 
> > If anyone has any suggestions of where I might begin with this that would
> > be great. Apologies if the questions seem a bit simple I want to make
> > sure I'm not misunderstanding things right at the beginning.
> > 
> > Many thanks
> > 
> > Olivia

-- 
*************************************************************
Dr. Jörg Saßmannshausen, MRSC
University College London
Department of Chemistry
Gordon Street
London
WC1H 0AJ 

email: j.sassma... at ucl.ac.uk
web: http://sassy.formativ.net

Please avoid sending me Word or PowerPoint attachments.
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