[CP2K:9919] SCF_GUESS

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

Hi

I don't have experience with the application of ROKS+SIC methods.
As Matt already mentioned, it is well possible that there are
multiple minima and the best you can do is to follow a chosen
solution. Monitoring that you don't have transitions between
solutions during MD.

regards

Juerg
--------------------------------------------------------------
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: Xiaoming Wang 
Sent by: cp... at googlegroups.com
Date: 01/26/2018 05:15AM
Subject: Re: [CP2K:9919] SCF_GUESS

Dear Prof. Hutter,
I encountered the same problem again. I am doing simple ENERGY calculations. I have reduced the EPS_SCF to 1.0E-8, but still the total energy I obtained are different for the two cases: one is using SCF_GUESS of ATOMIC, and the other is RESTART, where the restart wave function is from a converged one of a similar structure with several atoms slightly distorted.  Other features of my calculation are ROKS and SIC included.  I am wondering why those two setups give such different results. The energy difference can be as large as 0.01 Ha. Following is my input:
&GLOBAL
  PROJECT_NAME SS
  RUN_TYPE ENERGY
  PRINT_LEVEL MEDIUM
&END GLOBAL
&FORCE_EVAL
  METHOD QS
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    WFN_RESTART_FILE_NAME SS-RESTART.wfn
    MULTIPLICITY 3
    ROKS
    &SIC
     SIC_METHOD EXPLICIT_ORBITALS
     SIC_SCALING_A 0.30
     SIC_SCALING_B 0.00
    &END SIC
    &MGRID
      CUTOFF 400
      REL_CUTOFF 40
    &END MGRID
    &XC
      &XC_FUNCTIONAL PBE 
      &END XC_FUNCTIONAL
    &END XC
    &SCF
      MAX_SCF 20
      EPS_SCF 1.0e-8
      CHOLESKY INVERSE
      SCF_GUESS RESTART
      &OT
       ROTATION
       PRECONDITIONER FULL_KINETIC
       ENERGY_GAP 0.01
       LINESEARCH 3PNT
      &END OT
      &OUTER_SCF
       EPS_SCF 1.0e-8
       MAX_SCF 50
      &END OUTER_SCF
    &END SCF
  &END DFT   &SUBSYS
   ....   &END SUBSYS
&END FORCE_EVAL


Best,Xiaoming

On Friday, October 27, 2017 at 4:32:51 AM UTC-4, jgh wrote:Hi



SCF_GUESS (RESTART/ATOMIC) is just for the very first guess,

meaning the first SCF iteration in the first step of a MD.



For initial guesses within one calculation (one MD step to the

next) you have to use



FORCE_EVAL / DFT / QS / EXTRAPOLATION  xxxxx



In any case, if the final result depends on any of these

choices, you have another problem, e.g. your convergence criteria

is not strict enough, or one calculation did not converge within the 

given number of steps etc.



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: Xiaoming Wang 

Sent by: cp... at googlegroups.com

Date: 10/26/2017 05:28AM

Subject: [CP2K:9590] SCF_GUESS



Dear all,

For BAND, OPT or MD calculations, one usually sets SCF_GUESS to RESTART, which will use the WFN of the previous step as a initial guess. This will usually accelerate the convergence of the SCF loops. However, The result is different from that with SCF_GUESS sed to ATOMIC. I am confused why the final results depend on the initial guess of the wfn.

Best,Xiaoming







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