[CP2K:10014] Energy difference between CP2K and VASP energy calculation results of fcc Si
Ari Paavo Seitsonen
ari.p.s... at gmail.com
Wed Feb 21 20:13:13 UTC 2018
Dear brhr,
Adding to Jürg's answer, if I remember correctly in VASP the total energy
of the pseudo atoms (stored in the POTCAR files) is subtracted from the
total energy. So even if you could (you most likely cannot, the kind of
pseudo potentials is limited in both codes) calculate the total energy with
a consistent set of the other parametres, you should consider also the
energy of the isolated (spherical) atoms.
Greetings from Paris,
apsi
2018-02-21 12:30 GMT+01:00 <hut... at chem.uzh.ch>:
> Hi
>
> in descending order:
>
> - pseudopotentials
> - k-points
> - basis sets
>
> only if you would have all of this equal, you could have the same results.
>
> For comparing total energies with VASP you need to converge a VASP PAW
> result wrt cutoff and k-points and then do a CP2K GAPW all-electron
> calculation with the same k-point grid and with a converged basis set.
> With these settings total energies could be rather close.
>
> 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: brhr
> Sent by: cp... at googlegroups.com
> Date: 02/21/2018 12:16PM
> Subject: [CP2K:10014] Energy difference between CP2K and VASP energy
> calculation results of fcc Si
>
> Dear CP2K experts,
> I have a very rudimental (probably stupid) question.....
> Energy of face centered cubic Si which calculated by VASP
> found at VASPwiki example page (https://cms.mpi.univie.ac.at/
> wiki/index.php/Fcc_Si)
> is -4.8758538 eV when the lattice parameter is 3.9 angstrom.
> I also found fcc Si calculations at the CP2K tutorial pages.
> ( "Simple Static Energy and Force Calculation Using QUICKSTEP"(
> http://www.cp2k.org/tutorials:static_calculation)
> and "How To Converge The Multi-Grid Used in QUICKSTEP"(http://www.cp2k.
> org/tutorials:converging_grid) )
> Energy cutoff values, lattice parameters and XC functional are different
> between these VASP and CP2K cases,
> and SCF_MAX is set to 1 in the case of CP2K.
> So I calculated fcc Si energy with CP2K 5.1 setting the energy cutoff 240
> eV ~ 8.820 a.u., the lattice parameter 3.9 angstrom,
> XC functional PBE and SCF_MAX defaut value.
> The input file is the following:
> -----------------------------------------------------------------
> @SET twice_lp 7.80&GLOBAL
> PROJECT Si_bulk8
> RUN_TYPE ENERGY
> PRINT_LEVEL MEDIUM
> &END GLOBAL
> &FORCE_EVAL
> METHOD Quickstep
> &DFT
> BASIS_SET_FILE_NAME BASIS_SET
> POTENTIAL_FILE_NAME GTH_POTENTIALS
> &MGRID
> CUTOFF 8.820
> &END MGRID
> &QS
> EPS_DEFAULT 1.0E-10
> &END QS
> &SCF
> SCF_GUESS ATOMIC
> EPS_SCF 1.0E-6
> ADDED_MOS 10
> CHOLESKY INVERSE
> &SMEAR ON
> METHOD FERMI_DIRAC
> ELECTRONIC_TEMPERATURE [K] 300
> &END SMEAR
> &DIAGONALIZATION
> ALGORITHM STANDARD
> &END DIAGONALIZATION
> &MIXING
> METHOD BROYDEN_MIXING
> ALPHA 0.4
> BETA 0.5
> NBROYDEN 8
> &END MIXING
> &END SCF
> &XC
> &XC_FUNCTIONAL PBE
> &END XC_FUNCTIONAL
> &END XC
> &END DFT
> &SUBSYS
> &KIND Si
> ELEMENT Si
> BASIS_SET DZVP-GTH-PBE
> POTENTIAL GTH-PBE-q4
> &END KIND
> &CELL
> SYMMETRY CUBIC
> A ${twice_lp} 0.00 0.00
> B 0.00 ${twice_lp} 0.00
> C 0.00 0.00 ${twice_lp}
> &END CELL
> &COORD
> SCALED
> Si 0.00 0.00 0.00
> Si 0.00 0.50 0.50
> Si 0.50 0.50 0.00
> Si 0.50 0.00 0.50
> Si 0.75 0.25 0.75
> Si 0.25 0.25 0.25
> Si 0.25 0.75 0.75
> Si 0.75 0.75 0.25
> &END COORD
> &END SUBSYS
> &PRINT
> &TOTAL_NUMBERS ON
> &END TOTAL_NUMBERS
> &END PRINT
> &END FORCE_EVAL--------------------------------------------------
> ---------------
> A part of the result by CP2K 5.1 is
> -----------------------------------------------------------------
> SCF WAVEFUNCTION OPTIMIZATION Step Update method Time
> Convergence Total energy Change
> ------------------------------------------------------------
> ------------------
> 1 NoMix/Diag. 0.40E+00 0.2 3.06132393 -28.5675142867
> -2.86E+01
> 2 Broy./Diag. 0.40E+00 0.3 2.32214549 -28.7998050659
> -2.32E-01
> 3 Broy./Diag. 0.40E+00 0.3 0.58522732 -29.4698863750
> -6.70E-01
> 4 Broy./Diag. 0.40E+00 0.3 0.20998859 -29.2828168394
> 1.87E-01
> 5 Broy./Diag. 0.40E+00 0.3 0.12057075 -29.1932153866
> 8.96E-02
> 6 Broy./Diag. 0.40E+00 0.3 0.05618396 -29.1361561613
> 5.71E-02
> 7 Broy./Diag. 0.40E+00 0.3 0.01016729 -29.1363881842
> -2.32E-04
> 8 Broy./Diag. 0.40E+00 0.3 0.00251115 -29.1338276656
> 2.56E-03
> 9 Broy./Diag. 0.40E+00 0.3 0.00053053 -29.1364584302
> -2.63E-03
> 10 Broy./Diag. 0.40E+00 0.3 0.00012439 -29.1370164369
> -5.58E-04
> 11 Broy./Diag. 0.40E+00 0.3 0.00008751 -29.1372252303
> -2.09E-04
> 12 Broy./Diag. 0.40E+00 0.3 0.00001301 -29.1371970535
> 2.82E-05
> 13 Broy./Diag. 0.40E+00 0.3 0.00001000 -29.1371543754
> 4.27E-05
> 14 Broy./Diag. 0.40E+00 0.3 0.00000033 -29.1371468686
> 7.51E-06 *** SCF run converged in 14 steps ***
> Electronic density on regular grids: -32.0116716966
> -0.0116716966
> Core density on regular grids: 32.0008931651
> 0.0008931651
> Total charge density on r-space grids: -0.0107785315
> Total charge density g-space grids: -0.0107785315 Overlap
> energy of the core charge distribution: 0.00000000000000
> Self energy of the core charge distribution:
> -82.06393942512820
> Core Hamiltonian energy:
> 15.15717724613789
> Hartree energy:
> 46.02547467061829
> Exchange-correlation energy:
> -8.25223104355429
> Electronic entropic energy:
> -0.00362831666283
> Fermi energy:
> -0.03620657710631 Total energy:
> -29.13714686858875------------------------------------------
> -----------------------
> The obtained energy per atom is -29.13714686858875 / 8 =
> -3.64214335857359375 a.u. ~ -99.10776 eV
> This is very different from -4.8758538 eV.
> Could anyone interpret the difference between these results?
> Thank you in advance.
> brhr
>
>
>
>
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--
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Ari Paavo Seitsonen / Ari.P.S... at iki.fi / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
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