[ase-users] Constrained center of mass

[Elsebeth Schröder]

Dear ASE users,

I am looking at adsorbed molecules on a surface (at the moment using gpaw). I would like to include a constraint that fixes position of the center of mass of the molecule relative to the surface, or at least the center of mass of two of the atoms in the molecule. 

The (very) old dacapo version that had atomic position optimization imbedded in the dacapo code (i.e., before the optimization was lifted out into ASE) was able to do the latter and I wonder if this has also been included in ASE, or if anybody could help me how to write such a constraint. I have browsed the ASE documentation but didn't find anything that seemed useful.

Elsebeth 

=====================================================================                          
Elsebeth Schröder, prof.                                                                       
Dept. of Microtechnology and         tel.:   +46 31 772 8424                                   
Nanoscience (MC2)                    fax:    +46 31 772 3471                                   
Chalmers Univ. of Technology         e-mail: schroder at chalmers.se                              
SE-412 96 Gothenburg, Sweden         http://fy.chalmers.se/~schroder                           
=====================================================================