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[Bryce Meredig <bmeredig@gmail.com>]

Thanks for the reply. I read in more detail the way ABINIT handles non-primitive cells and I guess that chkprim 0 turns off some symmetry identification routines. I see why that would explain what I observe, but I guess I don't understand why ABINIT cannot still detect the same symmetry I had for the primitive cell...?

On Sat, Oct 24, 2009 at 10:01 AM, Quan Phung Manh <manhquank9@gmail.com> wrote:

Dear Bryce

I don't know how your full input is. But I think your problem comes from the keyword: chkprim 0. You doubled the cell, then Abinit symmetry finder found that the unit cell is not primitive. The multiplicity is  2. The use of non-primitive unit cells is allowed only when the input variable chkprim is 0. I guess you used this keyword to pass the error. That why you had P1.

Regards.

2009/10/22 <bmeredig@gmail.com>

Dear Abinit users,

I'm having symmetry issues... I'm working with a distorted fluorite cell that
should have I4/mmm symmetry. When I use these inputs:

typat 1 2 2
xred
0 0 0
0.25 0.25 0.25
0.75 0.75 0.75
acell
1.0 1.0 1.0 angstrom
rprim
0 2.785 2.745
2.785 0 2.745
2.785 2.785 0

The symmetry finder gives me, correctly, I4/mmm. However, when I simply double
the cell along the c direction so:

typat 1 1 2 2 2 2
xred
0 0 0
0 0 0.5
0.25 0.25 0.125
0.25 0.25 0.625
0.75 0.75 0.375
0.75 0.75 0.875
acell
1.0 1.0 1.0 angstrom
rprim
0 2.785 2.745
2.785 0 2.745
5.57 5.57 0

ABINIT then thinks I have P1 (non)symmetry. However, a tool such as FINDSYM at
http://stokes.byu.edu/cgi-bin/iso/findsym.cgi readily verifies that I still in
fact have I4/mmm symmetry. What could be wrong?

Thanks--
Bryce

--
Quan Phung Manh
Khoa Hoá học - ĐH Khoa học tự nhiên - 19 Lê Thánh Tông Hà Nội