[CP2K:5006] Why does the energy increase with the CUTOFF and REL_CUTOFF increases?

[hut... at chem.uzh.ch]

Hi

The GPW method is not variational in the grid cutoff.
The basis is build from Gaussian functions and the plan wave
grid is used as an auxiliary basis with a projection type
of algorithm.
See also the literature (Computer Physics Communications 167, 103-128 (2005))
on how relative cutoff and maximal cutoff are used and how they
determine the overall accuracy. There are also some older posts
on this.
Still, it is good that you make these tests and some of the
energy changes give you information on convergence.

regards

Juerg Hutter

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie                  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: cp... at googlegroups.com
From: Jingyun Ye 
Sent by: cp... at googlegroups.com
Date: 02/28/2014 03:21PM
Subject: [CP2K:5006] Why does the energy increase with the CUTOFF and REL_CUTOFF increases?

Hi, all

Is there anything wrong with my input? The results looks wired. The energy increases with the cutoff and rel_cutoff increases.  rel_cutoff ev   cutoff 30 40 50 60 300 -29578.432902300500 -29578.399159283300 -29578.398302912000 -29578.397241072300 350 -29578.227875777000 -29578.222463593800 -29578.226837753600 -29578.227605089900 400 -29578.238083660700 -29578.227586907200 -29578.227387661600 -29578.221229653600 450 -29578.165548334700 -29578.154977170300 -29578.152711011900 -29578.154695241800

&GLOBAL
  PROJECT .........
  RUN_TYPE GEO_OPT
  PRINT_LEVEL MEDIUM
&END GLOBAL
&FORCE_EVAL
  METHOD QS
  &SUBSYS
    &CELL
      A  14.8340  0.0000   0.0000
      B  7.41698  12.8466  0.0000
      C  7.41698  4.28220  12.1119
    &END CELL
    &COORD
     .........................
    &END COORD
    &KIND C
      BASIS_SET DZVP-MOLOPT-SR-GTH-q4
      POTENTIAL GTH-PBE-q4
    &END KIND
    &KIND H
      BASIS_SET DZVP-MOLOPT-SR-GTH-q1
      POTENTIAL GTH-PBE-q1
    &END KIND
    &KIND O
      BASIS_SET DZVP-MOLOPT-SR-GTH-q6
      POTENTIAL GTH-PBE-q6
    &END KIND
    &KIND Zr
      BASIS_SET DZVP-MOLOPT-SR-GTH-q12
      POTENTIAL GTH-PBE-q12
    &END KIND
  &END SUBSYS
  &DFT
    BASIS_SET_FILE_NAME ~/input/cp2k/cp2k-2.4.0/tests/QS/BASIS_MOLOPT
    POTENTIAL_FILE_NAME ~/input/cp2k/cp2k-2.4.0/tests/QS/GTH_POTENTIALS
    &QS
      EPS_DEFAULT 1.0E-7
    &END QS
    &MGRID
      CUTOFF 450
      NGRIDS 4
      REL_CUTOFF 60
    &END MGRID
    &SCF
      SCF_GUESS RESTART
      EPS_SCF 1.0E-05
      MAX_SCF 500
      &DIAGONALIZATION T
        ALGORITHM STANDARD
      &END DIAGONALIZATION
      &MIXING T
        ALPHA 0.5
        METHOD PULAY_MIXING
        NPULAY 5
      &END MIXING
      &PRINT
        &RESTART OFF
        &END RESTART
      &END PRINT
    &END SCF
    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
    &END XC
  &END DFT
&END FORCE_EVAL
&MOTION
  &GEO_OPT
    TYPE MINIMIZATION
    MAX_DR    1.0E-03
    MAX_FORCE 1.0E-03
    RMS_DR    1.0E-03
    RMS_FORCE 1.0E-03
    MAX_ITER 1000
    OPTIMIZER CG
    &CG
      MAX_STEEP_STEPS  0
      RESTART_LIMIT 9.0E-01
    &END CG
  &END GEO_OPT
&END MOTION


  
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