[CP2K-user] Unable to converge for perovskite calculation

[Jiapeng Liu]

Dear CP2K users,

I repost the problem with the expectation that anyone can help me to solve 
this. I would like to perform the DFT+U calculations for a small perovskite 
cubic cell, which contains 10 atoms in total. As a first step suggested by 
this group, I conduct the DFT without U firstly. However, the scf fails to 
converge even after 3 outer scf each with 200 steps. I am quite confused 
about this. Can anyone help me with this, your suggestions or advice are 
significantly appreciated. Thank you. Following is the input file

!*************************GLOBAL SETTINGS**********************************
&GLOBAL
  PRINT_LEVEL LOW
  PROJECT_NAME LCTN_exsolution
  RUN_TYPE CELL_OPT
  SAVE_MEM T
&END GLOBAL

!*************************MOTION SETTINGS**********************************
&MOTION
  &CELL_OPT
    OPTIMIZER LBFGS
    TYPE DIRECT_CELL_OPT
  &END CELL_OPT
&END MOTION

!************************FORCE_EVAL SETTINGS********************************
&FORCE_EVAL
  STRESS_TENSOR ANALYTICAL
  METHOD QS
!********************FORCE_EVAL -> DFT SETTINGS*****************************
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT_UCL
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    UKS T
    CHARGE 0
    MULTIPLICITY 2
!    PLUS_U_METHOD LOWDIN
!****************FORCE_EVAL -> DFT -> SCF SETTINGS**************************
    &SCF
      ADDED_MOS 100
      MAX_SCF 200
      EPS_SCF 1.0E-6
      SCF_GUESS RESTART
      &DIAGONALIZATION T
        ALGORITHM STANDARD
      &END DIAGONALIZATION
      &OUTER_SCF
        EPS_SCF 1.0E-5
        MAX_SCF 5
      &END OUTER_SCF
      &SMEAR T
        METHOD FERMI_DIRAC
        ELECTRONIC_TEMPERATURE [K] 300
      &END SMEAR
      &MIXING T
        METHOD BROYDEN_MIXING
        ALPHA 0.4
        BETA [bohr^-1] 2
        NMIXING 5
        NBUFFER 8
      &END MIXING
    &END SCF
!****************FORCE_EVAL -> DFT -> QS SETTINGS***************************
    &QS
      EPS_DEFAULT 1.0E-12
      EXTRAPOLATION USE_GUESS
      METHOD GAPW
    &END QS
!***************FORCE_EVAL -> DFT -> GRID SETTINGS**************************
    &MGRID
      NGRIDS 5
      CUTOFF [Ry] 600
      REL_CUTOFF [Ry] 60
    &END MGRID
!*****************FORCE_EVAL -> DFT -> XC SETTINGS**************************
    &XC
      FUNCTIONAL_ROUTINE NEW
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
    &END XC
!***************FORCE_EVAL -> DFT -> POISSON 
SETTINGS************************
    &POISSON
      POISSON_SOLVER PERIODIC
      PERIODIC XYZ
    &END POISSON
  &END DFT
!********************FORCE_EVAL -> SUBSYS 
SETTINGS***************************
  &SUBSYS
    &CELL
      ABC [angstrom] 3.857 3.857 7.714
      ALPHA_BETA_GAMMA [deg] 90 90 90
      PERIODIC XYZ
      MULTIPLE_UNIT_CELL 1 1 1
    &END CELL
    &KIND La
      ELEMENT La
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q11
    &END KIND
    &KIND Ca
      ELEMENT Ca
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q10
    &END KIND
    &KIND Ti
      ELEMENT Ti
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q12
!      MAGNETIZATION 3.0
    &END KIND
    &KIND Ni
      ELEMENT Ni
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q18
!      MAGNETIZATION 3.0
!      &DFT_PLUS_U T
!        L 2
!        U_MINUS_J [eV] 6.4
!      &END DFT_PLUS_U
    &END KIND
    &KIND O
      ELEMENT O
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q6
    &END KIND
    &TOPOLOGY
      COORD_FILE_NAME lctn_112.xyz
      COORD_FILE_FORMAT XYZ
      MULTIPLE_UNIT_CELL 1 1 1
    &END TOPOLOGY
  &END SUBSYS

!********************FORCE_EVAL -> PRINT 
SETTINGS****************************
  &PRINT
    &FORCES ON
    &END FORCES
  &END PRINT
&END FORCE_EVAL

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