[Wien] non-rectangular cell

[Mahbube Hortamani]

Dear Dr. Blaha

Peter Blaha wrote:

> I guess we don"t understand each other.
>
> I can see that the energy is decreasing. But I still don"t know for wich
> calculation it occurs.
> From your first struct file, I saw CXZ lattice with monoclinic angle.
> First of all only an angle gamma (not alpha) is allowed.
> Secondly, the calculations may simply be wrong because of the well known
> CXZ bug with monoclinic angle.

As I mentioned before the CXZ was not correct file please ignore of that file.
every detail that I sent was belong to P lattice with non rectangular cell.

> Now if the problem comes from a rectangular P calculation, my next
> suggestion was:
> a) You did not converge with -fc (but -cc or -ec) and thus your forces
> are not correct. Of course in such a case when you minimize the wrong
> forces, E-tot will rise.

I used of mini program with following command in order to minimized force.
    min_lapw -I -j  'runsp_lapw  -it -p -i 99  -fc 1.5'


>
> b) Forces can be "wrong", when R0 for a heavier element (Mn) is too large.
> While the R0 for Si might be ok, for Mn it might be not.

Be sure I will check for smaller R0 but you should consider I used of this value in rectangular cell
and it has not such a big influence.

>
> c) Could it be that you have broken the symmetry by some wrong movements
> of some atoms ? Also in such a case the forces might be wrong.
> (I'm surprised that right at the beginning you have such a low symmetry. I
> thought this is fcc-Si and one Mn is substituting one Si? It should not
> have  forces, but some higher symmetry???

This is not bulk calculation, this is a surface and I have 2 symmetry operation (inversion and
identity symmetry). this is Si surface with Si-dimer on top most layer + Mn as an adsorbate atom on
this surface.

>
> d) Why would you fix both, Mn and some (distant) Si atoms ?

We performed this calculation in order to find Potential Energy Surface for adsorbate atom then we
should fix the position of adatom, also we treat The  atoms in middle layer as a bulk for this
reason, atom 14-17 are fixed.

>
>
> I hope I could explaine what I want to do and what is my problem.

thank you for your attention,
Mahbube.
--
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Mahbube Hortamani

Fritz-Haber-Institut
der Max-Planck-Gesellschaft
Abteilung Theorie
Faradayweg 4-6
D-14 195 Berlin-Dahlem / Germany

Phone  : ++49-30-8413 4820
Fax    : ++49-30-8413 4701
E-mail : hortaman at fhi-berlin.mpg.de
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