Fermi-Dirac smearing and magnetism
mpol
polynsk... at gmail.com
Thu Jul 3 14:04:49 UTC 2014
Dear CP2k users,
We try to model a semiconducting material (the gap is close to zero) with CP2k.
The system has an even number of electrons and DFT-mGGA (TPSS functional with SR-MOLOPT-GTH BS
and GTH pseudopotentials for PBE functional) is used to describe the electronic structure.
It is practically impossible to converge the wavefunction of the system without smearing and thus
Fermi-Dirac smearing is used. And here an interesting issue arises: when
the smearing with electronic temperature of 1 K or 50 K is used, the
system is paramagnetic. However when the smearing with electronic
temperature of 300 K is used, the system becomes diamagnetic.
May it be an artifact caused by smearing (so the system is truly
paramagnetic at the room temperature) or it may be an evidence that the
quenching of the magnetic moment occurs and the system is diamagnetic
at the room temperature?
With best regards,
MP
P.S. An example input file:
&FORCE_EVAL
METHOD QS
&DFT
BASIS_SET_FILE_NAME [path]
POTENTIAL_FILE_NAME [path]
&MGRID
NGRIDS 5
CUTOFF 600
REL_CUTOFF 60
&END MGRID
&PRINT
&MO
ADD_LAST SYMBOLIC
COMMON_ITERATION_LEVELS 2000
EIGENVALUES
NDIGITS 8
OCCUPATION_NUMBERS
&EACH
GEO_OPT 1
QS_SCF 0
&END EACH
&END MO
&END PRINT
UKS .TRUE.
MULTIP 1
&QS
EPS_DEFAULT 1.0E-14
METHOD GPW
&END QS
&POISSON
PERIODIC XY
PSOLVER ANALYTIC
&END POISSON
&SCF
EPS_EIGVAL 1.0E-10
SCF_GUESS RESTART
EPS_SCF 5.0E-06
MAX_SCF 300
&DIAGONALIZATION
ALGORITHM STANDARD
MAX_ITER 5
&END DIAGONALIZATION
&MIXING
METHOD BROYDEN_MIXING
NBUFFER 8
ALPHA 0.2
BETA 1.0
&END MIXING
&SMEAR
METHOD FERMI_DIRAC
ELECTRONIC_TEMPERATURE 300.0
&END SMEAR
ADDED_MOS 32
&END SCF
&XC
&XC_FUNCTIONAL TPSS
&END XC_FUNCTIONAL
&vdW_POTENTIAL
DISPERSION_FUNCTIONAL PAIR_POTENTIAL
&PAIR_POTENTIAL
TYPE DFTD3
PARAMETER_FILE_NAME [path]
REFERENCE_FUNCTIONAL TPSS
CALCULATE_C9_TERM .TRUE.
&PRINT_DFTD SILENT
COMMON_ITERATION_LEVELS 100
&END
&END PAIR_POTENTIAL
&END vdW_POTENTIAL
&END XC
&END DFT
&SUBSYS
&CELL
PERIODIC XY
ABC 19.64800 51.04800 16.00000
&END CELL
&TOPOLOGY
&CENTER_COORDINATES .FALSE.
&END
&END TOPOLOGY
&COORD
[coords]
&END COORD
[KIND sections with BSs and PPs specified in the message]
&END SUBSYS
&END FORCE_EVAL
&GLOBAL
RUN_TYPE GEO_OPT
PRINT_LEVEL MEDIUM
&TIMINGS
THRESHOLD 0.000001
&END
&DBCSR
MM_DRIVER BLAS
&END
&END GLOBAL
&MOTION
&GEO_OPT
MAX_ITER 2000
&END
&END
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