CELL_OPT to obtain lattice parameters close to experimental values.
Vladimir Rybkin
rybk... at gmail.com
Fri Sep 22 09:27:42 UTC 2017
Dear ... ,
here is a couple of comments:
1) the results are not that bad bearing in mind all approximations made in
the PBE functional;
2) MOST IMPORTANTLY: one needs to converge the the calculations with
respect to k-points. In practice, as you are performing a Gamma-point
calculation, you should use a supercell, i.e. replicate your unit cell at
least twice in b and c directions.
3) Why are you using smearing: is it a metal?
4) MOLOPT basis sets are better suited to molecular calculations. Try GTH
basis sets.
5) GEO_OPT does not optimize the cell at all, that's not an option.
6) I don't think you need external pressure as soon as you get a reasonable
large cell.
Yours,
Vladimir
четверг, 21 сентября 2017 г., 11:02:59 UTC+2 пользователь
ganta.... at gmail.com написал:
>
> Hi all,
>
> I am trying to do cell optimization of a goethite FeOOH unit cell. The
> lattice parameters of the considered unit cell are a=9.91340 b=3.0128,
> c=4.58 ( the same values I used in cp2k).
>
> I have tested all three cases (direct cell opt, geo opt, MD) of the
> CELL_OPT and
>
> The cell optimized values are approximately a=9.33, b=3.063 c=4.179.
> *The experiment values of lattice constants are a=9.96 b=3.02 c=4.62. *
>
> *I want to obtain the optimized values close to expt. values. *
>
> In trail and error, I have used STESS_TENSOR NUMERICAL, I have disabled D3
> correction and I have also used zero pressure.
>
>
>
> Below is my input file.
> &Global
>
>
> PROJECT goethite_cellopt
>
>
> RUN_TYPE CELL_OPT
>
>
> PRINT_LEVEL LOW
>
>
> &END GLOBAL
>
>
>
>
>
> &FORCE_EVAL
>
>
> METHOD Quickstep
>
>
> STRESS_TENSOR ANALYTICAL
>
>
> &DFT
>
>
> BASIS_SET_FILE_NAME BASIS_MOLOPT
>
>
> POTENTIAL_FILE_NAME GTH_POTENTIALS
>
>
> CHARGE 0
>
>
> MULTIPLICITY 1
>
>
> &MGRID
>
>
> NGRIDS 5
>
>
> CUTOFF 600
>
>
> REL_CUTOFF 60
>
>
> &END
>
>
> &QS
>
>
> METHOD GPW
>
>
> EPS_DEFAULT 1.0E-12
>
>
> EXTRAPOLATION ASPC
>
>
> EXTRAPOLATION_ORDER 4
>
>
> &END
>
>
> &SCF
>
>
> SCF_GUESS ATOMIC
>
>
> MAX_SCF 1500
>
>
>
> EPS_SCF 1.0E-8
>
>
> &OUTER_SCF
>
>
> MAX_SCF 30
>
>
> EPS_SCF 1.0E-8
>
>
> &END
>
>
> ADDED_MOS 30
>
>
> CHOLESKY INVERSE
>
>
> &SMEAR ON
>
>
> METHOD FERMI_DIRAC
>
>
> ELECTRONIC_TEMPERATURE [K] 300
>
>
> &END SMEAR
>
>
> &DIAGONALIZATION
>
>
> ALGORITHM STANDARD
>
>
> &END DIAGONALIZATION
>
>
> &MIXING
>
>
> METHOD BROYDEN_MIXING
>
>
> ALPHA 0.1
>
>
> BETA 1.5
>
>
> NBROYDEN 8
>
>
> &END MIXING
>
>
> &END SCF
>
>
> &XC
>
>
> &XC_FUNCTIONAL PBE
>
>
> &END XC_FUNCTIONAL
>
>
> &VDW_POTENTIAL
>
>
> POTENTIAL_TYPE PAIR_POTENTIAL
>
>
> &PAIR_POTENTIAL
>
>
> PARAMETER_FILE_NAME dftd3.dat
>
>
> TYPE DFTD3
>
>
> REFERENCE_FUNCTIONAL PBE
>
>
> R_CUTOFF [angstrom] 15
>
>
> &END
>
>
> &END VDW_POTENTIAL
>
>
> &END XC
>
>
> &END DFT
>
>
>
>
>
> &SUBSYS
>
>
> &CELL
>
>
> ABC [angstrom] 9.91340 3.01280 4.58000
>
>
> PERIODIC XYZ
>
>
> &END CELL
>
>
> &TOPOLOGY
>
>
> COORD_FILE_NAME goethite_unitcell.xyz
>
>
> COORD_FILE_FORMAT XYZ
>
>
> &CENTER_COORDINATES T
>
>
> &END CENTER_COORDINATES
>
>
> &END
>
>
> &KIND H
>
>
> BASIS_SET DZVP-MOLOPT-SR-GTH
>
>
> POTENTIAL GTH-PBE-q1
>
>
> &END KIND
>
>
>
> &KIND Fe
>
>
>
> BASIS_SET DZVP-MOLOPT-SR-GTH
>
>
> POTENTIAL GTH-PBE-q16
>
>
> &END KIND
>
>
> &KIND O
>
>
> BASIS_SET DZVP-MOLOPT-SR-GTH
>
>
> POTENTIAL GTH-PBE-q6
>
>
> &END KIND
>
>
>
>
>
> &END SUBSYS
>
>
> &END FORCE_EVAL
>
>
>
>
>
> &MOTION
>
>
> &CELL_OPT
>
>
> OPTIMIZER BFGS
>
>
> MAX_ITER 5000
>
>
> KEEP_ANGLES T
> EXTERNAL_PRESSURE 1.01325 0 0 0 1.01325 0 0 0 1.01325
>
>
>
> &END
>
>
> &END
>
>
> Goethite unit cell
>
> 16
>
>
> Fe H O2
>
>
> Fe 1.446365 0.753200 4.357412
>
>
> Fe 8.467034 2.259600 0.222588
>
>
> Fe 3.510335 2.259600 2.067412
>
>
> Fe 6.403065 0.753200 2.512588
>
>
> H 8.912147 0.753200 2.752580
>
>
> H 1.001253 2.259600 1.827420
>
>
> H 5.957953 2.259600 0.462580
>
>
> H 3.955446 0.753200 4.117420
>
>
> O 7.940633 0.753200 1.305300
>
>
> O 1.972767 2.259600 3.274700
>
>
> O 6.929466 2.259600 3.595300
>
>
> O 2.983933 0.753200 0.984700
>
>
> O 9.400877 0.753200 3.682320
>
>
> O 0.512523 2.259600 0.897680
>
>
> O 5.469223 2.259600 1.392320
>
>
> O 4.444177 0.753200 3.187680
>
>
> Please let me know if you have any suggestions.
>
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