Unable to converge for perovskite calculation
Jiapeng Liu
Krack Matthias (PSI)
Hi
Without k points you will need a larger simulation cell, i.e. multiple unit cells, e.g. 4x4x2. A larger electronic temperature for the smearing might also help initially. With a larger cutoff, it might also be possible to use the default GPW method instead of GAPW in the beginning.
Matthias
From: cp...@googlegroups.com <cp...@googlegroups.com>
On Behalf Of Jiapeng Liu
Sent: Freitag, 22. November 2019 01:47
To: cp2k <cp...@googlegroups.com>
Subject: [CP2K:12529] Unable to converge for perovskite calculation
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****************************
&FORCES ON
&END FORCES
&END PRINT
&END FORCE_EVAL
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Jiapeng Liu
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Krack Matthias (PSI)
Hi
That result is not a surprise, since you did not follow my first and most important suggestion which was to employ multiple unit cells.
Matthias
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Jiapeng Liu
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Krack Matthias (PSI)
Hi Jiapeng
I am afraid that is not possible.
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