[Pw_forum] SCF correction compared to forces is large

[Tayebeh Roohande]

Dear all

I want to optimize the lattic  parameter of an BaSrCoFeO3 1*1*2
supercell but in output there is this warning"

SCF correction compared to forces is  large, reduce conv_thr"

I am very thankful any to solve this problem.


here is my input file:

CONTROL
   calculation = "relax",

pseudo_dir  = "/root/Desktop/work/ps",
  outdir      = "/root/Desktop/work/out",

nstep=150
/
&SYSTEM
  ibrav     = 6,
  celldm(1) =  7.4606

celldm(3)=2

  nat       = 10,
  ntyp      = 5,
  ecutwfc   = 29.41D0,
  ecutrho   = 290.D0,
 occupations = "smearing",
  smearing    = "methfessel-paxton",
  degauss     = 0.05D0,
nspin=2,
                   starting_magnetization(4)= 0.4
                   starting_magnetization(5)= 0.3
/
&ELECTRONS
  conv_thr    = 1.D-6,
  mixing_beta = 0.1D0,
electron_maxstep=500
/
&IONS
ion_dynamics = 'bfgs'
/
ATOMIC_SPECIES
Ba  137.32D0  Ba.pbe-nsp-van.UPF
Sr  87.62D0  Sr.pbe-sp-van.UPF
O  15.99D0  O.pbe-van_ak.UPF
Fe  55.84D0  Fe.pbe-nd-rrkjus.UPF
Co  58.93D0  Co.pbe-n-van_gipaw.UPF
ATOMIC_POSITIONS (alat)
 Sr                 0.50000000    0.50000000    0.50000000
 Co                 0.00000000    0.00000000    0.00000000
 O                  0.50000000    0.00000000    0.00000000
 O                  0.00000000    0.50000000    0.00000000
 O                  0.00000000    0.00000000    0.50000000
 Sr                 0.50000000    0.50000000    1.50000000
 Co                 0.00000000    0.00000000    1.00000000
 O                  0.50000000    0.00000000    1.00000000
 O                  0.00000000    0.50000000    1.00000000
 O                  0.00000000    0.00000000    1.50000000
K_POINTS {automatic}
 4 4 4 0 0 0


here is a part of out file:



     bravais-lattice index     =            6
     lattice parameter (alat)  =       7.4606  a.u.
     unit-cell volume          =     830.5349 (a.u.)^3
     number of atoms/cell      =           10
     number of atomic types    =            5
     number of electrons       =        74.00
     number of Kohn-Sham states=           44
     kinetic-energy cutoff     =      29.4100  Ry
     charge density cutoff     =     290.0000  Ry
     convergence threshold     =      1.0E-06
     mixing beta               =       0.1000
     number of iterations used =            8  plain     mixing
     Exchange-correlation      =  SLA  PW   PBX  PBC ( 1 4 3 4 0)
     EXX-fraction              =        0.00
     nstep                     =          150




     convergence has been achieved in   9 iterations

     Forces acting on atoms (Ry/au):

     atom    1 type  2   force =     0.00000000    0.00000000   -0.00081871
     atom    2 type  5   force =     0.00000000    0.00000000    0.00000000
     atom    3 type  3   force =     0.00000000    0.00000000    0.00000000
     atom    4 type  3   force =     0.00000000    0.00000000    0.00000000
     atom    5 type  3   force =     0.00000000    0.00000000   -0.00008303
     atom    6 type  2   force =     0.00000000    0.00000000    0.00081871
     atom    7 type  5   force =     0.00000000    0.00000000    0.00000000
     atom    8 type  3   force =     0.00000000    0.00000000    0.00000000
     atom    9 type  3   force =     0.00000000    0.00000000    0.00000000
     atom   10 type  3   force =     0.00000000    0.00000000    0.00008303

     Total force =     0.001164     Total SCF correction =     0.000127
     *SCF correction compared to forces is large: reduce conv_thr to
get better values
*
     bfgs converged in   3 scf cycles and   2 bfgs steps
     (criteria: energy < 0.10E-03, force < 0.10E-02)


Thanks in advance T.roohande

Ph.D of physics
University of Tarbiat modares
Tehran
Iran
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