Energy difference between CP2K and VASP energy calculation results of fcc Si
brhr
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.
( "Simple Static Energy and Force Calculation Using QUICKSTEP"(http://www.cp2k.org/howto:static_calculation)
and "How To Converge The Multi-Grid Used in QUICKSTEP"(http://www.cp2k.org/howto:converging_grid) )
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
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
This is very different from -4.8758538 eV.
Thank you in advance.
hut...@chem.uzh.ch
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...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------
-----cp...@googlegroups.com wrote: -----To: cp2k <cp...@googlegroups.com>
From: brhr
Sent by: cp...@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.
and "How To Converge The Multi-Grid Used in QUICKSTEP"(http://www.cp2k.org/tutorials:converging_grid) )
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brhr
Dear Professor Hutter and Dr. Seitsonen
Thank you for very instructive replies.
In fccSi file (This file is generated from http://www.vasp.at/vasp-workshop/examples/fccSi.tgz, which is linked by
the above mentioned VASPwiki page),
EATOM = 103.0669 eV, 7.5752 Ry
The total energy considering the psudo-atom energy may be 103.0669 - 4.8758 ~ +98.1910 eV
This value is pretty close to the CP2K results except for its sign...
Anyway I should reexamine the CP2K input.