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[Xavier Gonze <xavier.gonze@uclouvain.be>]

Dear Csaba Sz.,

The z coordinates of your xred input variable are wrong : usually they
vary between 0 and 1. Indeed beyond 1, the cell is repeated.
So, the coordinates  1/3 2/3   0.375   ,  1/3 2/3 1.375 corrsponds to  
the same point
in space (also 1/3 2/3 2.375).

Good luck,
Xavier

On 15 Jan 2009, at 20:52, cszakacs@mun.ca wrote:

> Hello all,
>
> Recently I started to use Abinit (so I am a very new user), and I  
> was going
> trough the examples. They were very useful and I figured out lots of  
> things,
> especially when I am dealing with bulk.
>
> Now, I want to move ahead and I am trying to construct a slab unit  
> cell for a
> wurtzite structure (ZnO) in order to build a 3d surface.
>
> I checked already the example 4 (with the Al surface) from the  
> tutorial, but I
> still don't understand some things.
>
> My approach is the following, I am starting from the bulk structure  
> to make a
> larger so called slab unit cell like this:
>
> acell  2*6.14 9.83
> rprim  1.0 0.0 0.0
>       -0.5 sqrt(0.75) 0.0
>       0.0 0.0 2.0
>
> #atom type
> ntypat 2
> znucl 30 8
> #def of atoms
> natom 8
> typat 1 1 2 2
>      1 1 2 2
>
> xred 1/3 2/3 0.0
>     2/3 1/3 0.5
>     1/3 2/3 0.375
>     2/3 1/3 0.875
>     1/3 2/3 1.375
>     2/3 1/3 1.875
>     1/3 2/3 2.375
>     2/3 1/3 2.875
>
> practically I am puting 2 bulks on the top of eachother.
>
> But I know that I am wrong because it gives me an error (two of the  
> atoms are
> located at the same point)
>
> And even if I change the acell c parameter, let's say I've doubled  
> it, nothing
> changes.
> And I am not sure even how the vacuum layer is defined, it should be  
> controlled
> by the rprim I guess, but what it does, it puts space between the  
> atoms..not
> between layers.
>
>
> Probably I am looking in a totally wrong direction.
> Maybe some of
> you ar more familiar with surface construction, so I would kindly  
> ask for your
> opinion or advice in this matter.
>
> Thank you
>
> Regards,
>
> --
> Csaba Sz.
> Memorial University
> Dept. of Chemistry
> St. John's, NL