[CPMD-list] Velocities in CPMD

[Juerg Hutter]

Hi

there is no straightforward way in CPMD to achieve what you
want. I suggest to follow this procedure.

1) Run a single step of MD with the following set up

MOLELCULAR DYNAMICS
MAXSTEP
 1
RESTART WAVEFUNCTION COORDINATES
TEMPERATURE
  300   <- or whatever your surface should be

This generates RESTART and GEOMETRY files.
Now edit the GEOMETRY file to change the velocities
of the particles according to your experiment.
Now restart the MD with the options

MOLELCULAR DYNAMICS
MAXSTEP
 1000
RESTART WAVEFUNCTION COORDINATES VELOCITIES GEOFILE
QUENCH ELECTRONS

The effect of this is:
IONIC coordinates are read from GEOMETRY
IONIC velocities are read from GEOMETRY
ELECTRON wavefunctions and velocities are read from RESTART
ELECTRON velocities are set to zero

hope this helps

Juerg

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 1 635 4491
Physical Chemistry Institute   FAX   : ++41 1 635 6838
University of Zurich           E-mail: hutter at pci.unizh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Thu, 4 Apr 2002, Diego Troya wrote:

> Hi all,
> 
>    I've been recently trying to use the VELOCITIES keyword in a molecular
> dynamics run. I want to collide fast atoms against surfaces. Despite the
> code seems to read the input velocities properly, when the run starts the
> initial velocities are always the same (apparently coming from a
> thermal distribution), no matter what is the velocity you specify for the
> incoming atom. I'm not using QUENCH IONS, so I don't understand why the
> input initial velocities are not considered in the calculation.
> 
> Has anybody any experience with this?
> 
> Thanks in advance,
> Diego.
> 
> Dr. Diego Troya
> Chemistry Department, Northwestern University
> 2145 Sheridan Road, 60208 Evanston, Il.
> Phone: 847 491 7189
> Fax: 847 491 7713
> 
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