energy jump in SCCS

[Geng Sun]

Dear CP2K users,

I am trying to use the SCCS solvent model to optimize a H2O molecule in solvent and calculate the solvation energy.

I found that during the structure optimization, the total energy jumps up almost 3 eV, but the structure of H2O still looks good.

Finally, with the energy obtained in solvent ( -17.07615353442375 a.u.) and energy in vacuum (-17.22203206260123), the solvation energy is positive.

Therefore, there must be something wrong in the calculations, but I can not figure it out.

grep "Total energy:" cp2k.out gives:

  Total energy:                                               -17.22994560779211
  Total energy:                                               -17.23016218028583
  Total energy:                                               -17.23052945533816
  Total energy:                                               -17.23057483762070
  Total energy:                                               -17.23059795728501
  Total energy:                                               -17.23061684603447
  Total energy:                                               -17.23062875959604
  Total energy:                                               -17.23063230147527
  Total energy:                                               -17.23063606787884
  Total energy:                                               -17.23458599053544
  Total energy:                                               -17.07789974445440
  Total energy:                                               -17.23050622895307
  Total energy:                                               -17.23059409756609
  Total energy:                                               -17.23153569898144
  Total energy:                                               -17.23062905094530
  Total energy:                                               -17.23063896643257
  Total energy:                                               -17.06258564479369
  Total energy:                                               -17.23061553671926
  Total energy:                                               -17.23064419320881
  Total energy:                                               -17.23017384159302
  Total energy:                                               -17.09997174618866
  Total energy:                                               -17.23053249119082
  Total energy:                                               -17.23061888501270
  Total energy:                                               -17.23062632201262
  Total energy:                                               -17.10641501376824
  Total energy:                                               -17.23063629047595
  Total energy:                                               -17.23099984646603
  Total energy:                                               -17.11100171504137
  Total energy:                                               -17.10215507558170
  Total energy:                                               -17.13946950681089
  Total energy:                                               -17.05320236101690
  Total energy:                                               -17.23214150951693
  Total energy:                                               -17.14172122406513
  Total energy:                                               -17.05319840556444
  Total energy:                                               -17.06170695684858
  Total energy:                                               -17.11231720859150
  Total energy:                                               -17.07455263629729
  Total energy:                                               -17.07623660559768
  Total energy:                                               -17.07963295606425
  Total energy:                                               -17.07859069368490
  Total energy:                                               -17.07694563368373
  Total energy:                                               -17.07637515123947
  Total energy:                                               -17.07632103460653
  Total energy:                                               -17.07605114342309
  Total energy:                                               -17.07615353442375

Here is the input file:

&FORCE_EVAL
   &DFT
      UKS
      BASIS_SET_FILE_NAME BASIS_MOLOPT_UCL
      BASIS_SET_FILE_NAME BASIS_MOLOPT
      POTENTIAL_FILE_NAME GTH_POTENTIALS
      &MGRID
         CUTOFF 400
         COMMENSURATE
      &END MGRID
      &QS
         EXTRAPOLATION PS
         EXTRAPOLATION_ORDER 3
         EPS_DEFAULT  1.0E-12
         MAP_CONSISTENT T
      &END QS
      &PRINT
         &SCCS ON
            &EACH
               QS_SCF 1
            &END EACH
         &END SCCS
      &END PRINT
      &SCCS
         ALPHA [N*m^-1] 0.02
         GAMMA [mN/m] 0.0
         BETA [GPa] -0.08
         DELTA_RHO 2.0E-5
         DERIVATIVE_METHOD CD5
         DIELECTRIC_CONSTANT 6.02
         EPS_SCCS 1.0E-10
         EPS_SCF 0.03
         MAX_ITER 100
         METHOD Andreussi
         MIXING 0.6
         &ANDREUSSI
            RHO_MAX 0.003
            RHO_MIN 0.0003
         &END ANDREUSSI
      &END SCCS
      &SCF
         EPS_SCF 1.0E-7
         MAX_SCF 31
         SCF_GUESS RESTART
         &OT
            ENERGY_GAP 0.002
            LINESEARCH 2PNT
            PRECONDITIONER FULL_ALL
            MINIMIZER DIIS
         &END OT
         &OUTER_SCF
            EPS_SCF 1.0E-7
            MAX_SCF 20
         &END OUTER_SCF
      &END SCF
      &XC
         &XC_FUNCTIONAL PBE
         &END XC_FUNCTIONAL
      &END XC
   &END DFT
   &SUBSYS
      &KIND H
         BASIS_SET TZVP-MOLOPT-GTH
         POTENTIAL GTH-PBE-q1
      &END KIND
      &KIND O
         BASIS_SET TZVP-MOLOPT-GTH
         POTENTIAL GTH-PBE-q6
      &END KIND
      &COORD
         O 7.424704500000000706e+00 9.621645000000000891e+00 1.106072519999999848e+01
         H 7.912573799999999657e+00 1.000790999999999897e+01 1.180680414000000056e+01
         H 6.473416799999999860e+00 9.760409999999998476e+00 1.119866495999999856e+01
      &END COORD
      &CELL
         PERIODIC XYZ
         A 1.641000000000000014e+01 0.000000000000000000e+00 0.000000000000000000e+00
         B 0.000000000000000000e+00 1.650000000000000000e+01 0.000000000000000000e+00
         C 0.000000000000000000e+00 0.000000000000000000e+00 1.824599999999999866e+01
      &END CELL
   &END SUBSYS
   &PRINT
      &FORCES ON
         LOG_PRINT_KEY T
      &END FORCES
   &END PRINT
&END FORCE_EVAL

I greatly appreciate any suggestions on fixing this.

Thank you very much.

Best Regards,

Geng

[Krack Matthias (PSI)]

Hi Geng

 

Such fluctuations are usually caused by numerical noise. A larger cutoff, e.g. 800 instead of 400Ry, will most likely resolve that issue.

 

HTH

 

Matthias

--
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+uns...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/be04892b-30f6-4654-b51a-5acc8228e885%40googlegroups.com.

[Tzu-Yao HSU]

Hi all,

I got similar problem as Geng, but my calculation is pure DFT energy evaluation.

During the SCF run, the polarisation energy abruptly jumped up to a positive value and the SCF convergence jumped down at certain convergence level .

Then the polarisation energy always stayed positive until the SCF run converged.

Here are my input file (.inp) and reduced output file (.out, grep 'Diag.' and 'Polarisation energy' then paste) .

My molecular structure (optimized.dat) was obtained by performing GEO_OPT in vacuum.

Further increasing the MGRID CUTOFF, EPS_SCF in SCCS section, simulation box size, and decreasing CUTOFFs in XC section do not change the converged energy.

Since the converged polarisation energy is always positive, I still wonder how may I improve my input file?

I appreciate any response to this problem.

Thank you very much

Best regards

Tzu-Yao

Matthias Krack於 2020年1月7日星期二 UTC+1下午7時40分51秒寫道：

To unsubscribe from this group and stop receiving emails from it, send an email to cp...@googlegroups.com.

[Krack Matthias (PSI)]

Hi Tzu-Yao

 

You may try smaller values for RHO_MAX and RHO_MIN. A cut-off of 600 Ry (maybe even 400 Ry) should large enough.

 

HTH

 

Matthias

To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+uns...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/9ba5de66-d129-4f24-8c09-139d9f834286%40googlegroups.com.

[Tzu-Yao HSU]

Thank you very much Matthias!

I made it work by lowering RHO_MIN. (Obtained negative polarisation energy instead of positive value)

However, if I use a cut-off of 600 Ry, I would still get a positive polarisation energy.

Tzu-Yao

Matthias Krack於 2020年6月4日星期四 UTC+2下午10時39分13秒寫道：

To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/9ba5de66-d129-4f24-8c09-139d9f834286%40googlegroups.com.