Hi Prof. P. Blaha
I need some help with supercell calculations. I'd like to investigate the
effect of replacing Se with Te in the system FeSe. Structure file is as shown
below.
FeSe
P LATTICE,NONEQUIV.ATOMS: 2129_P4/nmm
MODE OF CALC=RELA unit=ang
7.119735 7.119735 10.364585 90.000000 90.000000 90.000000
ATOM -1: X=0.25000000 Y=0.75000000 Z=0.00000000
MULT= 2 ISPLIT=-2
-1: X=0.75000000 Y=0.25000000 Z=0.00000000
Fe NPT= 781 R0=0.00005000 RMT= 2.1900 Z: 26.0
LOCAL ROT MATRIX: 0.7071068-0.7071068 0.0000000
0.7071068 0.7071068 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -2: X=0.25000000 Y=0.25000000 Z=0.23720000
MULT= 2 ISPLIT=-2
-2: X=0.75000000 Y=0.75000000 Z=0.76280000
Se NPT= 781 R0=0.00005000 RMT= 1.9400 Z: 34.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
16 NUMBER OF SYMMETRY OPERATIONS
-1 0 0 0.00000000
0-1 0 0.00000000
0 0-1 0.00000000
1
0-1 0 0.00000000
-1 0 0 0.00000000
0 0-1 0.00000000
2
0 1 0 0.00000000
1 0 0 0.00000000
0 0 1 0.00000000
3
1 0 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
4
-1 0 0 0.50000000
0 1 0 0.00000000
0 0 1 0.00000000
5
-1 0 0 0.50000000
0-1 0 0.50000000
0 0 1 0.00000000
6
0-1 0 0.50000000
-1 0 0 0.50000000
0 0 1 0.00000000
7
0 1 0 0.50000000
-1 0 0 0.00000000
0 0-1 0.00000000
8
0 1 0 0.00000000
-1 0 0 0.50000000
0 0 1 0.00000000
9
0-1 0 0.00000000
1 0 0 0.50000000
0 0-1 0.00000000
10
0-1 0 0.50000000
1 0 0 0.00000000
0 0 1 0.00000000
11
0 1 0 0.50000000
1 0 0 0.50000000
0 0-1 0.00000000
12
-1 0 0 0.00000000
0 1 0 0.50000000
0 0-1 0.00000000
13
1 0 0 0.50000000
0-1 0 0.00000000
0 0-1 0.00000000
14
1 0 0 0.00000000
0-1 0 0.50000000
0 0 1 0.00000000
15
1 0 0 0.50000000
0 1 0 0.50000000
0 0-1 0.00000000
16
Then I copy it to a new session and create a supercell 2X2X1 with lattice F.
The program recognizes 8 inequivalent atoms, each with two positions (total of
16 atoms). Then I replace the last atom of Se by Te so that I have a doping of
25% and set its RMT to 2 and the atomic number to 52. RMT_Fe=2.1 and
RMT_Se=1.96. Here I have a couple of questions. First, I wonder if we have to
label all inequivalent atoms (for instance, Fe1, Fe2, Se1, Se2, etc.) because
when I compute xnn, I got a warning like this
WARNING: Mult not equal. PLEASE CHECK outputnn-file WARNING: ityp not equal.
PLEASE CHECK outputnn-file WARNING: ityp not equal. PLEASE CHECK outputnn-file
NN created a new SFeSeTe.struct_nn file
NN created a new CASE.STRUCT_NN FILE
0.016u 0.000s 0:00.01 100.0% 0+0k 0+160io 0pf+0w
If I continue to x group I got another warning such as this:
warning: !!! Number of inequivalent atoms has changed. !!! Old value= 8 New
value= 6 warning: !!! Bravais lattice has changed.
sgroup found: 12 (C 2/m) [unique axis c] cell choice 2
Why? And then the program suggests to change the sgroup. If I don't accept and
continue I get an error in editinst step:
error: SFeSeTe.inst not consistent with Zedit SFeSeTe.inst and rerun lstart
afterwards or change Z in StructGen!
On the other hand, if I labeled the atoms, the warnings after xnn is executed
don't appear anymore. However, when I run sgroup, I got a warning:
warning: !!! Struct file is not consistent with space group found.
sgroup found: !!! Struct file is not consistent with space group found. Number
and name of space group: 2 (P -1)
which causes errors in forthcoming steps. Should I labeled them and why? What
is the correct procedure to avoid these warnings and perform supercell
calculations successfully. I'm a beginner with supercell calculations.
I have already read the manual but the information is not enough to solve this
problem. I also checked the wien list of problems. There are some similar to
mine but the warnings and errors are different. I'd appreciate any assistance
you may have.
Regards
Thanks
Israel Perez
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