[CP2K-user] [CP2K:11065] comparing CP2K-DFTB (5.1) and DFTB+ (18.2)
Thomas Kühne
tku... at gmail.com
Sat Dec 22 14:31:53 UTC 2018
Dear Wei Lai,
have you used explicit diagonalization or the default OT minimizer?
Do the fully converged SCC-results agree? If not please provide the
input file.
Merry Christmas,
Thomas
> Am 19.12.2018 um 19:09 schrieb Wei Lai <wei.w... at gmail.com>:
>
> Dear Juerg,
>
> I have done further testing and may be closer to find out the source of this discrepancy. Basically, non-SCC results are "consistent" between CP2K and DFTB+. Fore SCC-DFTB, they differ in whether to include SCC at the first scf (it also seems that DFTB+ applies non-scc scf first before applying SCC energy). I don't know the coding thoughts of SCC well enough but I am wondering which one of these two is the better way. Regarding why CP2K results are sensitive to ALPHA I guess there are many local energy minimums.
>
> Thanks, Wei
>
> CP2K:
> Parameters Li-Mulliken-charge H0-energy SCC-energy
> NonSCC full scf 0.737779 -417.18328600
> SCC-1scf 0.737779 -355.69044000 0
> SCC-2scf 0.720362 -361.83972460 0.137714872
>
> DFTB+:
> NonSCC full scf 0.737791 -417.18197790
> SCC-1scf 0.737791 -417.18197790 10.2841704
> SCC-2scf 0.711388 -417.10728727 9.561284596
>
> On Wed, Dec 19, 2018 at 9:50 AM Wei Lai <wei.w... at gmail.com <mailto:wei.w... at gmail.com>> wrote:
> 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 <mailto: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 <mailto:hut... at chem.uzh.ch>
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com <mailto:cp... at googlegroups.com> wrote: -----
> To: "cp2k" <cp... at googlegroups.com <mailto:cp... at googlegroups.com>>
> From: "Wei Lai"
> Sent by: cp... at googlegroups.com <mailto: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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==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany
tdku... at mail.upb.de
+49/(0)5251/60-5726
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