[CPMD-list] (no subject)

[Axel Kohlmeyer]

On Thu, 1 Mar 2007, qfzhang wrote:

ZQ> Hi,experts!
ZQ>     I want to use Ultra-soft pseudopotential for MD. And I really don't know the
ZQ>  format of the US-PP file. Can I use the US-PPs that for VASP in CPMD? 

cpmd supports the format as it is created by the uspp generation 
program from the vanderbilt group (either in binary or in text format).
see the manual and the CPMD test examples for details on how to specify
them properly in the input.
VASP uses a different format, so those files cannot be used.

ZQ>     Can you give me some suggestions or tricks on the MD run using US-PP? Thank 
ZQ> you!

the major issue with USPPs in CPMD is, that there is no (working) 
dual-grid support, so you have to increase the resolution of the
real space grid for better numerical stability. (e.g. by explicitely
specifying a proper density cutoff or increasing the value of DUAL
to 5-6 for very high accuracy (phonons) up to 10. of course
that will kill some of the advantages of USPPs (low memory consumption).
also, you have to be a bit more careful in choosing the ficitious mass
and time step for CP dynamics. other than that, there is not much of
a difference wrt to running MD simulations.

axel. 

ZQ> 
ZQ> 
ZQ>    Best wishes
ZQ>                                                     Zhang Qianfan
ZQ>                                                      2007-03-01
ZQ> 
ZQ> 
ZQ> _______________________________________________
ZQ> CPMD-list mailing list
ZQ> CPMD-list at cpmd.org
ZQ> http://cpmd.org/mailman/listinfo/cpmd-list
ZQ> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.