[Pw_forum] (no subject)

[Giovanni Cantele]

Raghani Pushpa wrote:
> dear users,
> i was doing the slab calculations and wanted to fix a few middle layers of
> the slab, but i don't find the option 'fixatom' in the new code
> (pw-2.0.1), as it used to be in the old version. could u tell me is there
> any option related to this in the version 2.0.1?
> 
> pushpa
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> 


 From pwdocs/INPUT_PW:

ATOMIC_POSITIONS { alat | bohr | crystal | angstrom }


   There are "nat" cards like the following

   X  x y z   {if_pos(1) if_pos(2) if_pos(3)}

where :

   X           Character: label of the atom as specified in ATOMIC_SPECIES
   x, y, z     Real: atomic positions
   if_pos:     Integer: component i of the force for this atom is
               multiplied by if_pos(i), which must be 0 or 1. Used to
               keep selected atoms and/or selected components fixed in a
               NEB, MD or optimization run



A few examples:

Si     0.1  0.2   0.3			This Si atom is relaxed during
                                         the optimization

Si     0.1  0.2   0.3    0  0  0        This Si atom is kept fixed
                                         during the optimization

Si     0.1  0.2   0.3    0  1  1        In this case only the x
                                         coordinate is kept fixed

Hope this helps

Giovanni

-- 




Dr. Giovanni Cantele
INFM-Coherentia and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. G
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910
Fax:   +39 081 676346
E-mail: Giovanni.Cantele at na.infn.it
Web: http://people.na.infn.it/~cantele