[Wien] Question about hand-made structure calculation

[Gerhard Fecher]

Are you making jokes ?
ok here comes the answer:

Even more worth -258978.490839 / -86326.201472
is only 2.9999986843276078023793624055916 and not 3
probably that is a new re-definition of the natural number 3

Ciao
Gerhard


-----Ursprüngliche Nachricht-----
Von: wien-bounces at zeus.theochem.tuwien.ac.at im Auftrag von Cara Watson
Gesendet: Fr 09.11.2007 20:22
An: wien at zeus.theochem.tuwien.ac.at
Betreff: [Wien] Question about hand-made structure calculation
 
Dear Wien2k users,

Recently I was trying to do ab initio calculations on a modified
Bismuth structure to get the total energies corresponding to different
atomic configurations for the purpose of potential fitting. And I
started with the hexagonal Bismuth data downloaded from ICSD which has
6 equivalent atoms within the unit cell, but instead of specifying the
space group R-3m, I initiated the structure with  6 inequivalent atoms
in this unit cell, then I used the internal parameters for these 6
atoms from the ICSD data. Then I ran the calculations, in NN, it
showed the nearest distance is around 5.789.. which is correct, but in
the outputnn file it says there should be only 3 inequivalent atoms
instead (as in the attached file), but I think the NN result should
show there is only one inequivalent atom, since the parameters are
copied from that bismuth data with R-3m symmetry! Could you please
help me with this confusion? Thanks!

What's more, I continued running initialization and ignoring the
warnings from "sgroup" and "symmetry" (and I rejected any structure
change generated by NN, sgroup, etc), at the end I was able to run the
SCF calculations. However, the generated bandstructure is totally
different (or at least mostly different) from the one got from the
ICSD bismuth data which had specified R-3m symmetry. And what's even
worse, the calculated total energy is around -258978.490839 Ry
compared to the actual total energy around -86326.201472 Ry. It seemed
the calculation turned out to be a total failure.

Then I went back and use XCrysden to inspect the structure file, it
looks just the same with that ICSD data by eye! Then why the great
difference in calculation? I'm totally lost! Could you please help me
with this? Thanks a lot!!!

Thanks,
Cara

Structure file of the "handmade" bismuth:

Title
P   LATTICE,NONEQUIV.ATOMS:  6
MODE OF CALC=RELA unit=ang
  8.569911  8.569911 22.325233 90.000000 90.000000120.000000
ATOM  -1: X=0.00000000 Y=0.00000000 Z=0.23400000
          MULT= 1          ISPLIT= 8
Bi         NPT=  781  R0=0.00000500 RMT=    2.8000   Z: 83.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM  -2: X=0.00000000 Y=0.00000000 Z=0.76600000
          MULT= 1          ISPLIT= 8
Bi         NPT=  781  R0=0.00000500 RMT=    2.8000   Z: 83.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM  -3: X=0.66667000 Y=0.33333000 Z=0.56733000
          MULT= 1          ISPLIT= 8
Bi         NPT=  781  R0=0.00000500 RMT=    2.8000   Z: 83.0
LOCAL ROT MATRIX:    0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
                     1.0000000 0.0000000 0.0000000
ATOM  -4: X=0.33333000 Y=0.66667000 Z=0.90067000
          MULT= 1          ISPLIT= 8
Bi         NPT=  781  R0=0.00000500 RMT=    2.8000   Z: 83.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM  -5: X=0.66667000 Y=0.33333000 Z=0.09933000
          MULT= 1          ISPLIT= 8
Bi         NPT=  781  R0=0.00000500 RMT=    2.8000   Z: 83.0
LOCAL ROT MATRIX:    0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
                     1.0000000 0.0000000 0.0000000
ATOM  -6: X=0.33333000 Y=0.66667000 Z=0.43267000
          MULT= 1          ISPLIT= 8
Bi         NPT=  781  R0=0.00000500 RMT=    2.8000   Z: 83.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
   6      NUMBER OF SYMMETRY OPERATIONS
-1 1 0 0.00000000
-1 0 0 0.00000000
 0 0 1 0.00000000
       1
-1 1 0 0.00000000
 0 1 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
 0-1 0 0.00000000
 1-1 0 0.00000000
 0 0 1 0.00000000
       4
 1 0 0 0.00000000
 0 1 0 0.00000000
 0 0 1 0.00000000
       5
 1 0 0 0.00000000
 1-1 0 0.00000000
 0 0 1 0.00000000
       6

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