[Pw_forum] Phonon Calculation error on AF system

Thu Aug 16 09:09:02 CEST 2007

Dear Trevor,

this is more appropriately posted to the pw_forum (also, I cannot
really take individual questions). I'll do it for you.

Your material is - I presume - an AF insulator, in your DFT-PBE
calculations (if it is not, then you shouldn't try to calculate its 
dielectric constant, that is used to predict the correct LO-TO 
splitting). Still, you use smearing to aid convergence, so the code 
think your system is a metal (and it is, if unoccupied states are
fractionally occupied), and it complains when you try to calculate the
dielectric response.

Now, you could turn off the smearing. Still, at least a
few months ago, the code was still not set up to do
the dielectric constant of spin-polarized insulators.
It should be an easy modification (and following
JCP 120,9934 (2004)) but we didn't try.

It is my understanding that the phonons outside gamma
would come out nevertheless correct, even with the
code in the present status, provided you remove the dielec=.true.
option (amybe someone else can confirm).

So you would get everything right, but for the phonon
at gamma, where you wouldn't have the LO-TO splitting (since
it requires the calculation of effective charges and dielectric
constant).

			nicola

Trevor A. Tyson wrote:
> Dear Dr. Nicola Marzari:
>     I have been trying to use PWScf to calculate the phonon modes (at 
> Gamma) for the oxide LaMnO3 (antiferromagnetic).  The SCF computation 
> work fine but the phonon calculation fails.  Below are the "run file" 
> and the output file "lmoAF.phG.out" indicating the error code.  Thanks 
> in advance for your help.
> Trevor A. Tyson
> 
> -------------------------------------------------------------
> Trevor A. Tyson
> Department of Physics
> New Jersey Institute of Technology
>  Room 484, Tiernan Hall
> 161 Warren Street
> University Heights
>  Newark, New Jersey 07102-1982
> Tel: (973) 642-4681
> FAX: (973) 596-5794
> E-MAIL: TYSON at ADM.NJIT.EDU
> WWW Page: http://web.njit.edu/~tyson/
>  ---------------------------------------------------------------------------- 
> 
> 
> 
> 
> 
> 
> ***************************************
> # how to run executables
> PW_COMMAND='/home/tyson/PWSCF/espresso-3.2/bin/pw.x'
> PH_COMMAND='/home/tyson/PWSCF/espresso-3.2/bin/ph.x'
> $ECHO
> $ECHO "  running pw.x as: $PW_COMMAND"
> $ECHO "  running ph.x as: $PH_COMMAND"
> $ECHO
> # self-consistent calculation
> cat > lmoAF.scf.in << EOF
>  &control
>     calculation='scf',
>     restart_mode='from_scratch',
>     prefix='lmoAF'
>     pseudo_dir = '/home/tyson/PWSCF/espresso-3.2/pseudo',
>     outdir='/home/tyson/PWSCF/espresso-3.2/tmp/'
>  /
>  &system
>     ibrav = 0,
>     celldm(1) = 10.8600,
>     nat=  20, ntyp= 5, ecutwfc = 25.0,  ecutrho=250.0,
>     occupations='smearing', smearing='gauss', degauss=0.005,
>     nspin=2,
>     starting_magnetization(1)=  0.0,
>     starting_magnetization(2)=  0.5,
>     starting_magnetization(3)= -0.5,
>     starting_magnetization(4)=  0.0,
>     starting_magnetization(5)=  0.0,
> 
> /
>  &electrons
>     mixing_beta = 0.7
>     conv_thr =  1.0d-8
>  /
> ATOMIC_SPECIES
>  La1 138.91   La.pbe-nsp-van.UPF
>  Mn1 54.938   Mn.pbe-sp-van.UPF
>  Mn2 54.938   Mn.pbe-sp-van.UPF
>  O1  15.999   O.pbe-van_ak.UPF
>  O2  15.999   O.pbe-van_ak.UPF
> 
> 
> CELL_PARAMETERS
> 1.00 0.00 0.00
> 0.00 1.3385 0.00
> 0.00 0.00 0.96336
> 
> 
> ATOMIC_POSITIONS {crystal}
>  La1  0.049    0.25    0.9922
>  La1  0.951    0.75    0.0078
>  La1  0.549    0.25    0.5078
>  La1  0.451    0.75    0.4922
>  Mn1  0.0      0.0     0.5
>  Mn1  0.5      0.0     0.0
>  Mn2  0.5      0.5     0.0
>  Mn2  0.0      0.5     0.5
>  O1   0.4874   0.25    0.0745
>  O1   0.9874   0.25    0.4255
>  O1   0.0126   0.75    0.5745
>  O1   0.5126   0.75    0.9255
>  O2   0.3066   0.0384  0.7256
>  O2   0.6934   0.9616  0.2744
>  O2   0.3066   0.4616  0.7256
>  O2   0.6934   0.5384  0.2744
>  O2   0.1934   0.9616  0.2256
>  O2   0.8066   0.0384  0.7744
>  O2   0.1934   0.5384  0.2256
>  O2   0.8066   0.4616  0.7744
> 
> K_POINTS automatic
> 2 2 2 0 0 0
> 
> 
> EOF
> $ECHO "  running the scf calculation...\c"
> $PW_COMMAND < lmoAF.scf.in > lmoAF.scf.out
> $ECHO " done"
> 
> # phonon calculation at Gamma
> cat > lmoAF.phG.in << EOF
> phonons of LaMnO3 AF at Gamma
>  &inputph
>   tr2_ph=1.0d-14,
>   prefix='lmoAF',
>   epsil=.true.,
>  amass(1) =  138.91,
>  amass(2) = 54.938,
>  amass(3) = 54.938,
>  amass(4) = 15.999,
>  amass(5) = 15.999,
>   outdir='/home/tyson/PWSCF/espresso-3.2/tmp',
>   fildyn='lmoAF.dynG',
>  /
> 0.0 0.0 0.0
> EOF
> $ECHO "  running the phonon calculation at Gamma...\c"
> $PH_COMMAND < lmoAF.phG.in > lmoAF.phG.out
> $ECHO " done"
> 
> 
> **************************************************************************
>  lmoAF.phG.out
> 
> 
>      Program PHONON    v.3.2    starts ...
>      Today is 15Aug2007 at 10: 2:42
> 
>      Ultrasoft (Vanderbilt) Pseudopotentials
> 
>      nbndx  =   106  nbnd   =   106  natomwfc =   152  npwx   =    3512
>      nelec  = 176.00  nkb   =   240  ngl    =   14863
> 
>      Check: negative/imaginary core charge=   -0.000002    0.000000
> 
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
> 
>      from phq_readin : error #         1
>      no elec. field with metals
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
> 
> 
>      stopping ...
> 
> 
> 
> 
> 

-- 
---------------------------------------------------------------------
Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu