[Pw_forum] Phonon calculation crash in orthorhombic cell.

[Miriam Marques]

  Dear PWSCF users,

  I am trying to perform a phonon calculation on a uniform grid of  
q-points for an orthorhombic metallic structure.

First, I did the scf calculation for a 16x16x16 Monkhorst-Pack grid  
and tried to calculate phonons on a uniform (4x4x4) grid via ldisp,  
but the program phonon stopped with the error "end of self consistent  
calculation. No convergence has been achieved" in the representation 4  
(mode 4) of the first q point different from gamma. (I am using  
tr2_ph=1.0d-12)
Surprisingly, when I did the scf calculation for a 13x13x13  
Monkhorst-Pack grid and then the phonon calculation via ldisp on a  
4x4x2 grid, the program ran (it crashed again when I tried the 4X4x8  
grid).

I attached the input for the first case.

   # self-consistent calculation
     cat > pcmcm.scf.in << EOF
  &control
     calculation='scf'
     restart_mode='from_scratch',
     pseudo_dir = '$PSEUDO_DIR/',
     outdir='$TMP_DIR/',
     prefix='pcmcm'
     tprnfor = .true.
     tstress = .true.
  /
  &system
     ibrav=  9, celldm(1) =6.089228715122, celldm(2) =0.86757351,  
celldm(3)= 2.5838341, nat=  4, ntyp= 1, nbnd= 20, ecutwfc = 30.0,  
ecutrho=300, occupations='smearing', smearing='methfessel-paxton',  
degauss=0.02
  /
  &electrons
     diagonalization='david'
     mixing_beta = 0.7
     conv_thr = 1.0D-10
/
ATOMIC_SPECIES
  P  30.973761 P.pw91-n-van.UPF
ATOMIC_POSITIONS crystal
  P 0.0000000000 0.0000000000 0.00000000000
  P 0.0000000000 0.0000000000 0.50000000000
  P 0.0000000000 0.0000000000 0.25000000000
  P 0.0000000000 0.0000000000 0.75000000000
K_POINTS {automatic}
16 16 16 0 0 0
EOF
     $ECHO "  running the scf calculation for P...\c"
     $PW_COMMAND < pcmcm.scf.in > pcmcm.scf.out
     $ECHO " done"

# phonon calculation on a (4 4 4) uniform grid of q-points
cat > pcmcm.ph.in << EOF
phonons of cmcm P
  &inputph
   tr2_ph=1.0d-12,
   prefix='pcmcm',
   ldisp=.true.,
   nq1=4, nq2=4, nq3=4
   amass(1)=30.973761,
   outdir='$TMP_DIR/',
   fildyn='pcmcm.dyn',
  /
EOF
$ECHO "  running the phonon calculation at Gamma...\c"
$PH_COMMAND < pcmcm.ph.in > pcmcm.ph.out



Thank you very much for your help,

Miriam.

----------------------
Miriam Marques
School of Physics
University of Edinburgh
----------------------