[Wien] bug in 'elast'? / temperature-dependent elastic constants
Olivier Delaire
delaire at caltech.edu
Thu Dec 15 02:17:27 CET 2005
Dear Wien2k users,
I am running into some problems with the script "init_elast". Actually, from browsing the forum archive, I agree with previous reports (around April 2005) that it seems the routine "genetempl.f" in SRC_elast is buggy...
I have to confess I am not using the latest version of the package but I haven't seen anything regarding 'elast' on the update-info page since the version I have.
Looking at the genetempl.f routine a little closer, it appears it might run into problems when the multiplicity of atoms is MULT>1 in init.struct. Has anyone experienced this?
More precisely, genetempl.f reads from init.struct to create the 'template' files tetra.templ and rhomb.templ. It does a loop on atoms
DO i=1,noa
READ(10,1030) indic,x,y,z ... reads the atom index and fractional coordinates,
WRITE(30,1040) indic,x,y,z ...then writes these to tetra.templ,
CALL xc2rh(x,y,z,lat,xr,yr,zr) ...calls xc2rh to modify them for rhombohedral,
WRITE(20,1040) indic,xr,yr,zr ...writes these to rhomb.templ
and then it reads 5 lines which it copies to tetra.templ and rhomb.templ.
These 5 lines are, I guess, supposed to be read the following lines:
1 line with MULT AND ISPLIT
1 line with NPT, RMT and Z
3 lines for local rotation matrix
and then it expects to read in the index and fractional coordinates fo the next atom type...
but that won't work if there are additional lines listing fractional coordinates of symetry equivalent atoms when MULT>2 ... or am I reading this wrong?
Does anyone have a version of genetempl.f that works for struct files containing symetry equivalent atoms?
thanks in advance,
Olivier Delaire.
PS:
In my case, genetempl causes the following error:
" PGFIO-F-231/formatted read/unit=10/error on data conversion.
File name = init.struct formatted, sequential access record = 29
In source file genetempl.f, at line number 52 "
when I run it with the following init.struct:
pure V supercell
P LATTICE,NONEQUIV.ATOMS: 5221_Pm-3m
MODE OF CALC=RELA unit=ang
11.324150 11.324150 11.324150 90.000000 90.000000 90.000000
ATOM 1: X=0.50000001 Y=0.50000002 Z=0.50000003
MULT= 1 ISPLIT= 2
V X NPT= 781 R0=0.00010000 RMT= 2.44 Z: 23.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -2: X=0.25000000 Y=0.25000000 Z=0.25000000
MULT= 8 ISPLIT= 4
-2: X=0.75000000 Y=0.75000000 Z=0.75000000
-2: X=0.75000000 Y=0.25000000 Z=0.25000000
-2: X=0.25000000 Y=0.75000000 Z=0.75000000
-2: X=0.75000000 Y=0.75000000 Z=0.25000000
-2: X=0.25000000 Y=0.25000000 Z=0.75000000
-2: X=0.25000000 Y=0.75000000 Z=0.25000000
-2: X=0.75000000 Y=0.25000000 Z=0.75000000
V 1NN NPT= 781 R0=0.00010000 RMT= 2.44 Z: 23.0
LOCAL ROT MATRIX: 0.4082483-0.7071068 0.5773503
0.4082483 0.7071068 0.5773503
-0.8164966 0.0000000 0.5773503
ATOM -3: X=0.50000000 Y=0.50000000 Z=0.00000000
MULT= 3 ISPLIT=-2
-3: X=0.00000000 Y=0.50000000 Z=0.50000000
-3: X=0.50000000 Y=0.00000000 Z=0.50000000
V 2NN NPT= 781 R0=0.00010000 RMT= 2.44 Z: 23.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -4: X=0.50000000 Y=0.00000000 Z=0.00000000
MULT= 3 ISPLIT=-2
-4: X=0.00000000 Y=0.50000000 Z=0.00000000
-4: X=0.00000000 Y=0.00000000 Z=0.50000000
V 3NN NPT= 781 R0=0.00010000 RMT= 2.44 Z: 23.0
LOCAL ROT MATRIX: 0.0000000 0.0000000 1.0000000
0.0000000 1.0000000 0.0000000
-1.0000000 0.0000000 0.0000000
ATOM 5: X=0.00000000 Y=0.00000000 Z=0.00000000
MULT= 1 ISPLIT= 2
V 5NN NPT= 781 R0=0.00010000 RMT= 2.44 Z: 23.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
48 NUMBER OF SYMMETRY OPERATIONS
(etc ...)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PPS:
Dear Peter,
Thank you for the advice. I plan to investigate both Fermi smearing and thermal expansion.
I don't think that this is the way to proceed. You suggest to take into
account only the "electronic temperature" via the Fermi function. Remember,
300K is only 2 mRy, so unless you go to very large temperatures, your
Fermi-function effects will be very small.
Unfortunately, in general this is a very small contribution and most likely
does not produce the effect you want to investigate.
For sure the thermal expansion is "more" important and you need to consider
this effect.
The best procedure is most likely to calculate the full phonon-dispersion
and I think from the slopes of the acustic modes you can get your info.
Using a "quasi-harmonic" approximation you can calculate the temperature
expansion "ab-initio" too and see how the slopes change with temperature
(volume). Of course such calculations are a bit expensive, but doable.
>> I have calculated some elastic constants for cubic metals using the "elast"
>> package of Wien2k. I am mostly interested in the shear modulus, which came out
>> in pretty good agreement with experimental values. So far I have been using
>> the tetrahedron integration method in lapw2. I was wondering wether it would
>> make sense to try and calculate the temperature-dependence of these elastic
>> constants using the Fermi smearing technique, with varying smearing
>> temperatures? I guess I could also introduce the thermal expansion 'by hand',
>> by modifying the structure.
>> Are there fundamental limitations to this approach or caveats I should be
>> aware of?
>> Thanks in advance for sharing your experience or insights.
>>
>> Olivier.
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
>
>
P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671 FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/
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