The ABINIT Users Mailing List ( CLOSED )

["Aldo Humberto Romero" <aromero@qro.cinvestav.mx>]

It seems to me that still the systems is not well converged..
0.25 GPa still is large... usually a good convergence should be
less than 0.01GPa.. but in any case, this is not too bad
and I do not think it is responsible for the problems you are
having.

Now with respect to the LO-TO splitting, did you check the
splitting on the gamma calculation?.. you should start
from there... no looking directly at the phonon dispersion..

On the other hand, when you plot the
DOS from anaddb, did you try to see what happen to small Q values?
let say (0.001, 0, 0) ... compare the values you get from the
anaddb calculation at Gamma with the ones you got from your
calculation... you will see the splitting (hopefully)...
could you send the output of the Gamma calculation? probably that
will help.

regards

-aldo.


-> == DATASET 14
-> ==================================================================
->
->
->
->  Real(R)+Recip(G) space primitive vectors, cartesian coordinates
-> (Bohr,Bohr^-1):
->
->  R(1)=  0.0000000  5.2250000  5.2250000  G(1)= -0.0956938  0.0956938
-> 0.0956938
->
->  R(2)=  5.2250000  0.0000000  5.2250000  G(2)=  0.0956938 -0.0956938
-> 0.0956938
->
->  R(3)=  5.2250000  5.2250000  0.0000000  G(3)=  0.0956938  0.0956938
-> -0.0956938
->
->  Unit cell volume ucvol=  2.8529153E+02 bohr^3
->
->  Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01
-> degrees
->
->
->
->   getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  48  48  48
->
->          ecut(hartree)=     50.000   => boxcut(ratio)=   2.04075
->
->
->
->
->
-> Cartesian components of stress tensor (hartree/bohr^3)
->
->   sigma(1 1)=  8.32143159E-06  sigma(3 2)=  0.00000000E+00
->
->   sigma(2 2)=  8.32143159E-06  sigma(3 1)=  0.00000000E+00
->
->   sigma(3 3)=  8.32143159E-06  sigma(2 1)=  0.00000000E+00
->
->
->
->
->
-> -Cartesian components of stress tensor (GPa)         [Pressure=
-> -2.4482E-01
-> GPa]
->
-> - sigma(1 1)=  2.44824938E-01  sigma(3 2)=  0.00000000E+00
->
-> - sigma(2 2)=  2.44824938E-01  sigma(3 1)=  0.00000000E+00
->
-> - sigma(3 3)=  2.44824938E-01  sigma(2 1)=  0.00000000E+00
->
->
->
->
->
->
================================================================================
->
-> == DATASET 15
-> ==================================================================
->
->
->
->
->
->  Real(R)+Recip(G) space primitive vectors, cartesian coordinates
-> (Bohr,Bohr^-1):
->
->  R(1)=  0.0000000  5.2500000  5.2500000  G(1)= -0.0952381  0.0952381
-> 0.0952381
->
->  R(2)=  5.2500000  0.0000000  5.2500000  G(2)=  0.0952381 -0.0952381
-> 0.0952381
->
->  R(3)=  5.2500000  5.2500000  0.0000000  G(3)=  0.0952381  0.0952381
-> -0.0952381
->
->  Unit cell volume ucvol=  2.8940625E+02 bohr^3
->
->  Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01
-> degrees
->
->
->
->  getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  48  48  48
->
->          ecut(hartree)=     50.000   => boxcut(ratio)=   2.03103
->
->
->
-> One thing more, when we plot the phonon dispersion curve for full BZ using
-> anaddb code, then we got positive frequencies at gamma point but in phonon
-> dispersion curve, we did not see any LO-TO separation, what will be
-> reason?,
-> One more, our frequencies are less in magnitude around 30 cm-1 less at
-> gamma
-> point as compared to experimental.
->
-> At gamma, i got around 342 cm-1, but expt. is 365 cm-1 ..
->
-> Your suggestion is welcomed.
-> kind regards
-> sanjeev
-> Kind
->
-> 2009/9/11 Anglade Pierre-Matthieu <anglade@gmail.com>
->
->> > What is the final stress?
->> Pressure= -8.5022E-01 GPa.
->>
->>
->> --
->> Pierre-Matthieu Anglade
->>
->
->
->
-> --
-> S. K. Gupta
-> PhD Candidate,
-> Dept. of Physics, Bhavnagar University.
-> Bhavnagar, 364 022., Gujarat, India.
->


-- 

Prof. Aldo Humberto Romero
CINVESTAV-Unidad Queretaro
Libramiento Norponiente 2000
CP 76230, Queretaro, QRO, Mexico
tel: 442 211 9909
fax: 442 211 9938

email: aromero@qro.cinvestav.mx
        aldorome@gmail.com
www: qro.cinvestav.mx/~aromero