[gpaw-users] Inplane force != zero

[Ask Hjorth Larsen]

Dear Duy Le

On Tue, 1 Jun 2010, Duy Le wrote:

> Dear All,I was relaxing 5 layer of Cu(111). For (1x1x5) slab, everything is
> great. However, for (5x5x5) slab, It is weird that the in-plane components
> of forces (in Oxy plane) are not zero (they should be zero because
> of symmetry). 
> I don't know what causes the problem (or maybe not).
> Any comment will be great!

How nonzero are they?  Is the system symmetric also with respect to the 
structure of grid points?

Regards
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