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[g930102@ccit.edu.tw]

Dear Jorge, 

Please drop my previous E-mail, because of typo.

You forgot to set kptopt3 as 2. 

Here is my results just modified your input. 

Phonon wavevector (reduced coordinates) : 0.00000 0.00000 0.00000 
Phonon energies in Hartree : 
8.966314E-04 8.966330E-04 1.208473E-03 2.074450E-03 2.074450E-03 
2.790341E-03 2.790343E-03 3.445115E-03 4.485473E-03 
Phonon frequencies in cm-1 : 
- 1.967879E+02 1.967882E+02 2.652292E+02 4.552891E+02 4.552892E+02 
- 6.124091E+02 6.124094E+02 7.561153E+02 9.844476E+02 

So, It is not the problems of yours and other people's issues. 

Best regards, 

======================================================= 
Lu Fu-Fa, Doctoral Student, E-mail: g930102@ccit.edu.tw 
Department of Applied Physics 
Chung Cheng Institute of Technology (CCIT), Taiwan 
======================================================= 

-- Original Message --
From: Jorge Iniguez <jiniguez@nist.gov>
To: forum@abinit.org
Send: 2003-08-08
Subject: [abinit-forum] phonons of hexagonal systems: probable bug

Dear abinitioners,

We have found what seems to be bug in the calculation of phonons of
hexagonal systems. Input and output files go attached.

We have studied MgB2, which has 3 atoms per unit cell and space group
P6_3/mmm.  At the Gamma point, this system should have four different
optical phonon frequencies, two of them being doubly degenerate.  When we
try to calculate them, abinit correctly recognizes four (as opposed to
nine) irreducible perturbations:

 The list of irreducible perturbations for this q vector is:
    1)  idir= 1 ipert= 1
    2)  idir= 3 ipert= 1
    3)  idir= 1 ipert= 2
    4)  idir= 3 ipert= 2

However, the final result is a list of frequencies...

  Phonon wavevector (reduced coordinates) :  0.00000  0.00000  0.00000
 Phonon energies in Hartree :
   8.954702E-04  1.138484E-03  1.197535E-03  2.116134E-03  3.353738E-03
   3.641500E-03  4.411735E-03  4.837036E-03  5.507493E-03
 Phonon frequencies in cm-1    :
-  1.965330E+02  2.498684E+02  2.628285E+02  4.644378E+02  7.360604E+02
-  7.992168E+02  9.682638E+02  1.061607E+03  1.208755E+03

.. that does not show the expected degeneracies!!  I could only briefly
look for the bug, but did not succeed, so I turn to the experts out there :)

Cheers,
Jorge

PS: I guess that the nonzero acoustic frequencies are to be attributed to
the problem described in the FAQ...


------------------------------------------------------------------------------
   Jorge Iniguez             NIST Center for Neutron Research
                             100 Bureau Drive, Mail Stop 8562
                             Gaithersburg, MD 20899-8562
                             Phone: 1-301-975-8367 Fax: 1-301-921-9847
                             E-mail address: jiniguez@nist.gov
                             http://www.ncnr.nist.gov/staff/jorge
------------------------------------------------------------------------------

___________________________________
NOCC, http://nocc.sourceforge.net

Attachment: MgB2phonon.out
Description: Binary data

# MgB2, which has 3 atoms per unit cell and space group P6_3/mmm.
acell 5.7690981162E+00 5.7690981162E+00 6.6066862442E+00 
angdeg 90 90 120 
xred 
0 0 0 
1/3 2/3 1/2 
2/3 1/3 1/2 

natom 3 
ntypat 2 
znucl 12 5 
type 1 2*2 

# xc, cutoff and k points 
ixc 1 
# ecut 1000 eV 
ecut    30.0           # Maximal kinetic energy cut-off, in Hartree
ngkpt 9 9 7 
nshiftk 1 
shiftk 2*0.0 0.5 

occopt 3 
tsmear 0.1 eV 

nstep 50 

##### 

ndtset 2 
jdtset 1 3 

### DS 1 Getting very well converged wave functions (needed for RF calcs) 

tolvrs1 1.0d-18 
kptopt1 1 
iscf1 5 
prtden1 1 
prtwf1 1 

### DS3 Response function calculation: E-field perturbation and phonons 

rfphon3 1 # Atomic displacement perturbation calc activated 
rfatpol3 1 3 # All atoms will be displaced 
#rfelfd3 3 # E-field perturbation calc activated 
rfdir3 1 1 1 # All three directions considered 

nqpt3 1 
qpt3 0.0 0.0 0.0 # Gamma point calc 

getwfk3 1 
#getddk3 2 
kptopt3   3               # Automatic generation of k points,
                          # no use of symmetries to decrease 
                          # the size of the k point set.

tolvrs3 1.0d-7 
iscf3 5 # Self-consistent calc using algthm 5