[CPMD-list] Problem about CONSTRAINT!

[Axel Kohlmeyer]

On Sat, 24 Dec 2005, Yang Zhenyu wrote:

YZ>  Dear CPMD users:
YZ>     
YZ>       I don't understand the structure of CONSTRAINT.

up front just a general remark, if you need detailed information,
that is not yet covered in the manual, please have a look at
the source code. many hints on how it works and what it done
are added as comments.

in the case of the CONSTRAINT file there even _is_ a little hint 
about the format in the manual.

YZ> If I give the constraint as:
YZ> 
YZ>   CONSTRAINTS
YZ>    FIX STRUCTURE
YZ>    1
YZ>        DIST 1 2 1.3856 GROWTH 0.001
YZ>   END CONSTRAINTS
YZ> 	
YZ>   I will get the file CONSTRAINT like this:
YZ> 
YZ>       1     1        -8.4551629000E-01    1.3876000000E+00
YZ>       2     1        -8.6635689677E-01    1.3896000000E+00
YZ>       ........skipped
YZ> 
YZ>   Would you please explain these results for me? 
YZ>   What does each column represent for and what is the units?

the columns are timestep number (NFI), constraint number, constraint
force and contraint value. the latter two are in atomic units.
you seem to be using a timestep of 2 a.u. because your constraint
is increased by 0.002 in each step. note, that GROWTH is the change
per unit of the timestep and not per step.

YZ>   And I have another question:
YZ>   Can CPMD do potential energy surface scanning?

not automatically, but it should be very simple to write
a small program or script that generates a series of input
files that you can run sequentially (using the wavefunction
from the previous step, but not the coordinates).

regards,
     	axel.

YZ>   Would you please give me some hints and references?
YZ>  
YZ>  
YZ>   Any suggestions will be appreciated!
YZ> 				
YZ> 
YZ> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡
YZ> ¡¡Best Regards
YZ> 
YZ> ¡¡Yang Zhenyu				
YZ>   State Key Laboratory of Nonlinear Mechanics (LNM)
YZ>   Institute of Mechanics, Chinese Academy of Sciences
YZ>   No.15 Beisihuanxi Road
YZ>   Beijing 100080, P. R. China
YZ>   FAX: 010-62579511
YZ> ¡¡yangzy at lnm.imech.ac.cn
YZ> ¡¡2005-12-24
YZ> 
YZ> 
YZ> _______________________________________________
YZ> CPMD-list mailing list
YZ> CPMD-list at cpmd.org
YZ> http://cpmd.org/mailman/listinfo/cpmd-list
YZ> 

-- 
=======================================================================
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
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.