[Pw_forum] constraints

[Lorenzo Paulatto]

In data 09 novembre 2009 alle ore 14:32:52, ali kazempour  
<kazempoor2000 at yahoo.com> ha scritto:

> Dear All
> I want to fix the distance between  two atom during relaxation , the  
> distance is 1.98 , but the code crash and the error is
>      target =   3.67419827
>      dmax   =   2.79062000
>
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      from init_constraint : error #         1
>      the target for constraint 1 is larger than the largest possible  
> value
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> why does it happen and what can I do?

Dear Ali,
the constraint is in unit of celldm(1), in your specific case you have  
asked the two atoms to be about 16 Angstrom apart, which is impossible in  
periodic boundary conditions with such a unit cell.

best regards


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Lorenzo Paulatto
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