[CP2K-user] [CP2K:11062] comparing CP2K-DFTB (5.1) and DFTB+ (18.2)
Wei Lai
wei.w... at gmail.com
Wed Dec 19 14:50:39 UTC 2018
Dear Juerg,
Thanks for your suggestion. Parameters I chose previously converged the
results reasonably. To be more systematic, I tried the following
combinations without specifying RCUT (I was doing that to make sure it's
less than 1/2 of the box size). Comparison of these with those I presented
earlier still suggests strong sensitivity to ALPHA and difference from
DFTB+.
Thanks, Wei
Accuracy GMAX ALPHA Li-Mulliken-charge H0-energy SCC-energy
1.00E-06 21 0.583 0.57183 -414.5978042 8.302909355
1.00E-10 21 0.583 0.57183 -414.5978042 8.302909355
1.00E-14 21 0.583 0.57183 -414.5978042 8.302909355
1.00E-14 61 0.583 0.57183 -414.5978033 8.302910247
1.00E-14 101 0.583 0.57183 -414.5978027 8.302910732
1.00E-14 101 0.35 (default) 0.572372 -414.6135268 8.288678932
On Wed, Dec 19, 2018 at 3:41 AM <hut... at chem.uzh.ch> wrote:
> Hi
>
> the parameter in the EWALD section are not very user friendly
> (for historical reasons). In your case you should not keep
> RCUT at a small value and change ALPHA.
> It is better to use the default (RCUT calculated from EWALD_ACCURACY
> and ALPHA internally).
> Also you have to make sure that GCUT is big enough for your system
> to give converged values.
> With all these settings you should see the same behaviour as in DFTB+.
>
> regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter Phone : ++41 44 635 4491
> Institut für Chemie C FAX : ++41 44 635 6838
> Universität Zürich E-mail: hut... at chem.uzh.ch
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com wrote: -----
> To: "cp2k" <cp... at googlegroups.com>
> From: "Wei Lai"
> Sent by: cp... at googlegroups.com
> Date: 12/19/2018 04:50AM
> Subject: [CP2K:11061] comparing CP2K-DFTB (5.1) and DFTB+ (18.2)
>
> Dear CP2K users and developers,
>
> I was testing the DFTB functionality of CP2K and comparing it to DFTB+.
> I was using Li2O (324 atoms) as an example and the CP2K input file is shown
> in the following (without the full coordinates).
>
> I found CP2K-DFTB results are very sensitive to the choice of Ewald
> (SPME which is the only Ewald method available for DFTB) parameter (ALPHA
> in A^-1). For a RCUT of 6 A, an estimate of ALPHA is usually 3.5/6=0.583.
> These results actually suggest indeed this is a good estimate.
> ALPHA Li-Mulliken-charge H0-energy Repulsive energy
> SCC-energy Tot energy
> 0.64 0.571831 -414.5978261 1.790186269
> 8.302889648 -404.5047502
> 0.583 0.57183 -414.5978042 1.790186269
> 8.302909311 -404.5047086
> 0.5 0.57183 -414.5978156 1.790186269
> 8.302899133 -404.5047302
> 0.35 0.572372 -414.6135268 1.790186269
> 8.288678932 -404.5346616
> 0.22 0.610178 -415.6039561 1.790186269
> 7.126741326 -406.6870285
> 0.219 0.611188 -415.6274692 1.790186269 7.090867312
> -406.7464156
>
> On the other hand, DFTB+ (using Ewald instead of SPME) results are NOT
> very sensitive to ALPHA. I am not sure what is the unit of ALPHA in DFTB+
> but I tried several values. A value of 0.219 (hand tuned) in CP2K gave
> similar results to those in DFTB+ with an automatic ALPHA value.
> ALPHA Li-Mulliken-charge H0-energy Repulsive energy
> SCC-energy Tot energy
> auto 0.61175023 -415.6390952 1.790189279 7.070521175
> -406.7783847
> 0.338 0.61175319 -415.6391637 1.790189279 7.07041506
> -406.7785594
> 0.64 0.6117653 -415.6394434 1.790189279 7.069981919
> -406.7792722
> 1 0.61178357 -415.6398657 1.790189279
> 7.069327807 -406.7803486
>
> I am puzzled by this comparison and wondering if you have any insight on
> this.
>
>
> Thanks, Wei
>
> &GLOBAL
> PROJECT Li2O
> RUN_TYPE ENERGY_FORCE
> PRINT_LEVEL LOW
> &END GLOBAL
>
> &FORCE_EVAL
> STRESS_TENSOR ANALYTICAL
> METHOD QS
> &DFT
> &QS
> METHOD DFTB
> &DFTB
> SELF_CONSISTENT T
> DO_EWALD T
> DISPERSION F
> &PARAMETER
> SK_FILE Li Li ./Li-Li.skf
> SK_FILE Li O ./Li-O.skf
> SK_FILE O Li ./O-Li.skf
> SK_FILE O O ./O-O.skf
> &END PARAMETER
> &END DFTB
> EPS_DEFAULT 1.0E-12
> EXTRAPOLATION ASPC
> EXTRAPOLATION_ORDER 2
> &END QS
>
> &SCF
> SCF_GUESS RESTART ! can be used to RESTART an interrupted
> calculation
> MAX_SCF 100
> EPS_SCF 1.0E-7
> ADDED_MOS 216
> CHOLESKY INVERSE
> &SMEAR ON
> METHOD FERMI_DIRAC
> ELECTRONIC_TEMPERATURE [K] 300
> &END SMEAR
> &MIXING
> METHOD DIRECT_P_MIXING
> ALPHA 0.1
> &END
> &END SCF
>
> &POISSON
> PERIODIC XYZ
> &EWALD
> EWALD_TYPE SPME
> ALPHA .64
> GMAX 21
> RCUT 5
> &END EWALD
> &END
> &END DFT
>
> &SUBSYS
> &CELL
> PERIODIC XYZ
> A 13.9765253067 0.0000000000 0.0000000000
> B 0.0000000000 13.9765253067 0.0000000000
> C 0.0000000000 0.0000000000 13.9765253067
> &END CELL
>
> &COORD
> Li 1.1647105 1.1647105 1.1647105
> Li 1.1647105 1.1647105 5.8235526
> Li 1.1647105 1.1647105 10.4823942
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