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["Anglade Pierre-Matthieu" <anglade@gmail.com>]

The simulation cell is periodical. This means that there is "six"
distances between you atoms. And only one of them is fixed by xcart.


On 4/16/07, Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> Hi all,
>
> Now, I use the following input file to compulate the optimum interatomic
> distance of two H atoms in H_2 molecular:
>
> -------------
> ndtset 21
> xcart:  -0.5  0.0 0.0
>         0.5  0.0 0.0
> xcart+  -0.025 0.0 0.0
>         0.025 0.0 0.0
> getwfk  -1
> nband    1
> acell 10 10 10
> ntypat 1
> znucl 1
> natom 2
> typat  1 1
> ecut 10.0
> nkpt 1
> nstep 10
> toldfe 1.0d-6
> diemac 1.0
> diemix 0.5
> -------------
>
> But I feel so wondering about the following things:
>
> Since the parameter *xcart* has set the positions of H atoms, why should
> I must also give the acell parameter at the same time.  I mean, with the
> the parameter *xcart*, we can already determine the distance between the
> two H atoms.  I've read the abinit's *Complete list of input variables*
> and cann't understand this thing.
>
> Furthermore, for the case I posted here, it only use the parameter
> acell instead of using it combinating with the parameter *rprim*, why?
>
> Thanks in advance.
>
> Hongyi Zhao
> GnuPG DSA: 0xD108493B


--
Pierre-Matthieu Anglade