Bad condition number R_COND = 2.214E-19

[Mithun M]

Dear All, 

Please see the error I received while optimizing a geometry.

Bad condition number R_COND = 2.214E-19 (smaller than the machine working precision) 

Please also see the full input here. 

&GLOBAL
  PROJECT H2O
  RUN_TYPE GEO_OPT
  PRINT_LEVEL LOW
&END GLOBAL
&FORCE_EVAL
  METHOD QS
  &SUBSYS
    &CELL
      ABC 25 25 25
    &END CELL
    &COORD

.......................................

&END COORD
    &KIND H
      BASIS_SET TZVP-GTH
      POTENTIAL GTH-PBE-q1
    &END KIND
    &KIND O
      BASIS_SET TZVP-GTH
      POTENTIAL GTH-PBE-q6
    &END KIND
    &KIND C
      BASIS_SET TZVP-GTH
      POTENTIAL GTH-PBE-q4
    &END KIND
    &KIND N
      BASIS_SET TZVP-GTH
      POTENTIAL GTH-PBE-q5
    &END KIND

  &END SUBSYS
  &DFT
    BASIS_SET_FILE_NAME BASIS_SETS
    POTENTIAL_FILE_NAME POTENTIAL
    &QS
      EPS_DEFAULT 1.0E-7
    &END QS
    &MGRID
      CUTOFF 200
      NGRIDS 4
      REL_CUTOFF 30
    &END MGRID
    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-05
      MAX_SCF 200
      &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 200
    OPTIMIZER CG
    &CG
      MAX_STEEP_STEPS  0
      RESTART_LIMIT 9.0E-01
    &END CG
  &END GEO_OPT
  &CONSTRAINT
    &FIXED_ATOMS
      COMPONENTS_TO_FIX XYZ
      LIST 1
    &END FIXED_ATOMS
  &END CONSTRAINT
&END MOTION

I look forward in hearing from you all. Thanks in Advance.

With Regards 

Mithun M 

[Thomas Kühne]

Dear Mithun M, 

certainly EPS_DEFAULT (at least 10E-10, better 10E-12) is not low enough und CUTOFF (280, better 320+ Ry) too low. 

Also, I would also reduce EPS_SCF (~10E-6, when using traditional diagonalization). 

Best, 

Thomas Kühne

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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

thomas...@upb.de

+49/(0)5251/60-5726

[ChStCo]

For anyone looking this up, this is probably due to the usage of Pulay mixing.

https://github.com/cp2k/cp2k/issues/2360