[CPMD-list] One more time monoclinic cell...

[Przemyslaw Dopieralski]

Hello

I read all posts about monoclinic cell and etc
but I still don't now how to exactly do it correctly with coordinates,
dimension and angles...

What I did:

CELL ABSOLUTE DEGRE

I've got my crystal:
a 10.9   alpha 90         inv            a 5.5     alpha  102
b 5.5    beta 102        ----->          b 14.6    beta    90
c 14.6   gamma 90                        c 10.9    gamma   90

and then I switched x y z ----> y z x

Someone told me that this is the best idea. But now I'm not so sure.
I calculated some monoclinic crystal - it looks ok. Then I checked
neighbour cell in vmd 1.8.4a22 with pbctools.tcl script and I find out
that some atoms are very close - the reason of my inversion of
coordinates and because of definition in this script xy plane. But when I
did my inversion - It's easy to proof that some points will be out of
plane xy and out of cell.

eg   (x y z)    ------------->    (y z x)
     (-2 0 14)  ------------->    (0 14 -2)

First point is inside the cell but after inversion (vmd treat xy plane as
a base of cell) is out of cell!!!!!!

But molden4.2 also show neighbour cell and in this program everythin is ok
- probably molden is able to find out what is the base of the cell xy
plane or for eg xz plane? And molden multiply the main cell in different
way than vmd program. But now I don't know how cpmd multiply the main
cell? Probably in the same way how do this vmd. So bad for me!!!!!

Or maybe I should do something like that: (change only a and b dimensions
and alpha nad betha angles)

a 10.9   alpha 90         inv            a 5.5     alpha  102
b 5.5    beta 102        ----->          b 10.9    beta    90
c 14.6   gamma 90                        c 14.6    gamma   90

and then I switched x y z ----> y x z

Or maybe should I switch only alpha and betha and leave the rest?
I'm don't know the source of cpmd program and now I can't find the best
way. I computed some monclinic crystals with my first example (rotational
inversion of everything) and program didn't complain that something is
wrong!!!! But I think that something was.

Now I'm little embarrassed


best regards,
Przemyslaw Dopieralski
University of Wroclaw
The Faculty of Chemistry
Theoretical Group of prof. Z.Latajka

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