[CPMD-list] what's the units of velocity?

[Axel Kohlmeyer]

On Fri, 16 Nov 2007, Axel Kohlmeyer wrote:

ZX> On Thu, 15 Nov 2007, #ZHU XI# wrote:
ZX> 
ZX> ZX>  
ZX> ZX> Dear cpmd users
ZX> ZX>  
ZX> ZX> can anybody tell me what's the units of  the velocity in 
ZX> ZX> "VELOCITIES ... END VELOCITIES
ZX> ZX> Section: &ATOMS"
ZX> ZX>  in the manual I can't find it.

ZX> the units in the input file follow
ZX> the internal units of cpmd, i.e. they
ZX> are in hartree atomic units. the only

on second thought, there may be a complication.
depending on which version of CPMD you are
using, it may actually happen, that your
velocities are rescaled to the value of
TEMPERATURE in the CPMD input file.
please note that those velocities are not used,
if you use a RESTART. as was pointed out by
somebody else, your best shot in controlling
the velocities on input is to use 
RESTART GEOFILE COORDINATES VELOCITIES ...
and then set the velocities (in atomic units)
in the file GEOMETRY (note, _not_ GEOMETRY.xyz).

please let us know, whether this is helpful
or tell us what you want to achieve, so that
we can make better suggestion.

the main recommendation (if it is not in the
manual, read the source code) remains. it may
be a bit complicated at the beginning, but it
will pay off in the long run. ;-)

cheers,
    axel.


ZX> exceptions are (most) length related 
ZX> parameters, where the ANGSTROM flag
ZX> changes triggers those values converted
ZX> from angstrom based units to atomic units
ZX> upon reading the input file. for details,
ZX> please have a look at the source code.
ZX> 
ZX> cheers,
ZX>    axel. 
ZX> 
ZX> ZX>  
ZX> ZX> Thanks in advance.
ZX> ZX> 
ZX> 
ZX> 

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