Bug in the cell-optimization
leit... at matcalc.de
Mon Sep 7 10:03:28 UTC 2009
the following part of the input file ndescribes my unit cell:
A 2.7 0.0 2.7
B 0.0 2.7 2.7
C 2.7 2.7 0.0
Si 0.00 0.00 0.00
Si 1.35 1.35 1.35
Than CP2K performes a coordinat transformation:
CELL_UC| Vector a [angstrom] 3.818 0.000 0.000 |a|
CELL_UC| Vector b [angstrom] 1.909 3.307 0.000 |b|
CELL_UC| Vector c [angstrom] 1.909 1.102 3.118 |c|
CELL_UC| Angle (b,c), alpha
CELL_UC| Angle (a,c), beta
CELL_UC| Angle (a,b), gamma [degree]:
However the Si coordinates remain at the positions:
1 1 Si 14 0.000000 0.000000 0.000000
2 1 Si 14 1.350000 1.350000 0.350000
And this is of course not correct, because the periodic images are now
arranged in a wong way.
On 7 Sep., 11:50, Teodoro Laino <teodor... at gmail.com> wrote:
> Dear Xujroman,
> what do you call "atomar basis". When the cell is rotated and aligned
> along the X,Y and Z axis the atomic coordinates are too...
> I don't see any evidence for the bug you're claiming to have found.
> Of course fee free to attach an input file that reproduces this error.
> xujroman wrote:
> > Dear CP2K users,
> > I am performing a cell optimization using Cell_Opt and Geo_Opt for
> > bulk Si.
> > However, I recognized a bug during the setup of the unit cell.
> > If the starting cell vectors are given along arbitrary directions,
> > CP2K performes a coodinate transformation so that the first cell
> > vector (A) points along the x-axis. However, the atomar basis in the
> > unit cell is not transformed. That leads to a completely different
> > (wrong) atomic structure taking the periodic boundary conditions into
> > account.
> > The most simple way to avoid this bug, is to use cell vectors in such
> > a way that the A vector is parallel to the x-axis.
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