[QE-users] Phonons for a metal with DFT+U at finite q-points

[asukserm at ictp.it]

Dear QE developer and users:

I am trying to calculate phonons for a metal with DFT+U at finite q-points
(different from Gamma) with the ph.x code. With a few exceptions (very low
U), the self-consistent iteration of the phonon calculation does not
converge.
My system is a SrCoO3 which is a metal and ferromagnetic material. I use a
DFT+U calculation for considering the magnetic atom (Co) including the
smearing method for the metal system. I have tried to vary the parameters,
such as U-parameter, k-point grid = 4x4x4 and 8x8x8, degauss of smearing,
and pseudopotential types.
A representative set of SCF and PH inputs are below.
Do you have a suggestion or a method to solve this problem?
Thank you in advance.

Akkarach Sukserm
ICTP, Italy
asukserm at ictp.it

----------------------------------------------------------------------
&CONTROL
    calculation   = "scf"
    forc_conv_thr =  1.00000e-04
    nstep         = 100
    outdir        = "./temp/"
    prefix        = "prefix"
    pseudo_dir    = "./PP_PAW_PBE"
/
&SYSTEM
    degauss        =  1.00D-02 	# vary 0.01, 0.02, 0.05, 0.08
    ecutrho        =  7.20D+02
    ecutwfc        =  8.00D+01
    ibrav   = 0, nat   = 5
    nspin  = 2, ntyp = 3
    occupations = "smearing" , smearing = "marzari-vanderbilt"
    starting_magnetization(2) =  0.50D0
    lda_plus_u          = .TRUE.
    hubbard_u(2)        =  3.00D0	# vary U= 1.25 and 3.00 eV
/

&ELECTRONS
    conv_thr         =  1.0e-08
    diago_david_ndim = 4
    diagonalization  = "david"
    mixing_beta      =  0.7D0
    mixing_mode  = "plain", startingpot = "atomic", startingwfc =
"atomic+random"
/
K_POINTS {automatic}
 8  8  8  0 0 0			# vary kp-mesh = 4x4x4 and 8x8x8

CELL_PARAMETERS {bohr}
   7.216934286   0.000000000   0.000000000
   0.000000000   7.216934286   0.000000000
   0.000000000   0.000000000   7.216934286

ATOMIC_SPECIES	# vary (1) PAW-PBE, (2) PAW-PBEsol, (3) USPP-PBEsol
Sr     87.62000  Sr.pbe-spn-kjpaw_psl.1.0.0.UPF
Co     58.93320  Co.pbe-spn-kjpaw_psl.0.3.1.UPF
O      15.99940  O.pbe-n-kjpaw_psl.1.0.0.UPF

ATOMIC_POSITIONS {crystal}
Sr      0.000000   0.000000   0.000000
Co      0.500000   0.500000   0.500000
O       0.500000   0.500000   0.000000
O       0.500000   0.000000   0.500000
O       0.000000   0.500000   0.000000
----------------------------------------------------------------------
This is my ph.x input:
----------------------------------------------------------------------
Phonon of SrCoO3 at q = 0, 0, 0.25 #NAME TAG
&inputph
tr2_ph=1.0d-12,
amass(1)=87.62000,
amass(2)=58.93320,
amass(3)=15.99940,
prefix='prefix',
alpha_mix(1)=0.7D0 		# Vary 0.5 and 0.7
outdir='./temp/'
fildyn='./ SrCoO3_q.dynq',
/
0.0 0.0 0.25
----------------------------------------------------------------------
This is my ph.x output:
---------------------------------- PH.out ----------------------------
Representation #   1 mode #   1

     Self-consistent Calculation
      iter #   1 total cpu time :  2300.3 secs   av.it.:  17.2
      thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  9.086E-03

      iter #   2 total cpu time :  2384.5 secs   av.it.:  29.1
      thresh= 9.532E-03 alpha_mix =  0.700 |ddv_scf|^2 =  1.768E+01

      iter #   3 total cpu time :  2469.9 secs   av.it.:  29.9
      thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  1.807E+01

      iter #   4 total cpu time :  2533.8 secs   av.it.:  20.9
      thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  4.797E+01

      iter #   5 total cpu time :  2607.1 secs   av.it.:  24.9
        thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  1.311E+02


      iter #  98 total cpu time : 21889.7 secs   av.it.: 138.5
      thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  1.431E+49

      iter #  99 total cpu time : 22224.4 secs   av.it.: 139.3
      thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  4.764E+49

      iter # 100 total cpu time : 22563.4 secs   av.it.: 140.9
      thresh= 1.000E-02 alpha_mix =  0.700 |ddv_scf|^2 =  1.497E+50

     End of self-consistent calculation
     No convergence has been achieved
------------------------- DONE --------------------------