[Wien] berryphase

[Oleg Rubel]

Dear Shahrbano,

it's good to hear that everything worked with the fresh install. I am 
also interested to trace the origin of your previous problems, but I 
cannot reproduce the error. If you still have an access to the previous 
installation and can reproduce both correct and incorrect results, try 
to switch packages one-by-one, e.g. replace only BerryPI and see whether 
it makes a difference. Then do the same with W2W, WIEN2K. This way you 
can narrow down the reason.

> Would you give me some clue to reach the goal sooner?

As far as I know, there is an internal relaxation in GaN wurtzite, which 
leads to slightly different Ga-N bond lengths (in c-direction and 
off-axis). Maybe the spontaneous polarization (Ps) is referred to a 
difference in polarization between two structures with relaxed and 
unrelaxed internal degrees of freedom? But I do not know for sure. How 
big is the value of Ps reported in the literature? By looking at the 
change of polarization when doing the effective charge calculations, you 
can guess how large the displacement should be to produce Ps.

In any case, I would think what is the *measurable* quantity related to 
change of polarization in GaN and try to calculate that.

> PS: We detected that init.sh ha a bug. If the version of the installed
> numpy is 1.6.2, the init.sh works fine. But, if the version is different
> depending on the linux version, e.g., numpy 1.4.1, then init.sh script
> tries to install numpy 1.6.2 on .local directory. This is not necessary,
> as already bumpy 1.4.1 is installed. Although the installation on .local
> directory is successful by init.sh, but init.sh cannot uses it, because
> it is not installed in the default path. So, for such a case, we changed
> 1.6.2 to 1.4.1 in init.sh to prevent its stop in changing the .bashrc
> automatically. We just thought that you maybe in next version would like
> to fix this small bug.

We suspected that BerryPI may not be compatible with earlier versions of 
numpy (before 1.6.2), but I don't think we actually tested it against 
numpy 1.4.1. The is the reason why init.sh is so picky. If you confirm 
that it works for you with numpy 1.4.1, we can loosen this requirement.


Thank you
Oleg