Total dipole/Wannier centers print in cp2k 2.3

[Jana]

Dear all,

I've been told I can get a total dipole file containing delta dipoles and these can be postprocessed via FT from a CPMD utility (and unit conversion) to obtain vibrational frequencies.

(This is an attempt to get a comparison as I've got reasonable IR spectrum simply from NORMAL_MODES where all the modes fit but for some reason the only one most characteristic frequency is strangely shifted like 500 cm-1 to low frequencies...this happens only in one of my several model systems. I've been trying to improve convergence criteria or basis sets or adding vdw correction but either no help or no convergence even after like more than one week on the wall...)

To get this I should run MD and print out TOTAL_DIPOLE, with reference to centers of atomic charges. I've tried to get dipoles and wannier centres according to what I've found while searching this google group, but I have only managed to get it run with ENERGY calculation, not MD, and as it is just a trial and error I got a bit lost and cannot really see what am I doing wrong. Could you please somebody help?

...

&MOTION

 &MD

    ENSEMBLE NVT

    STEPS 1000

    TIMESTEP 0.5

    TEMPERATURE   300.0

    &THERMOSTAT

       TYPE NOSE

       REGION GLOBAL

       &NOSE

         LENGTH 3

         YOSHIDA 3

         MTS 2

       &END

    &END

  &END MD

&END MOTION

&FORCE_EVAL

  METHOD QS

  &DFT

&LOCALIZE

    METHOD CRAZY

    OPERATOR BERRY

 &END LOCALIZE

&PRINT

 &LOCALIZATION

        &WANNIER_CENTERS MEDIUM

                FILENAME =water2.wannier

                &EACH

                MD 1

                &END EACH

        ADD_LAST

        COMMON_ITERATION_LEVELS 3

        &END

        &MOLECULAR_DIPOLES HIGH

        &END MOLECULAR_DIPOLES

        &TOTAL_DIPOLE MEDIUM

                FILENAME =water2.dip

                &EACH

                MD 1

                &END EACH

        REFERENCE COM

        PERIODIC TRUE

        COMMON_ITERATION_LEVELS 3

        &END TOTAL_DIPOLE

 &END

&END PRINT

   BASIS_SET_FILE_NAME GTH_BASIS_SETS

    POTENTIAL_FILE_NAME GTH_POTENTIALS

    &MGRID

      CUTOFF [Ry] 450

    &END MGRID

    &QS

      METHOD GPW

    &END QS

    &SCF

      SCF_GUESS RESTART

      MAX_SCF 100

      EPS_SCF 1.0e-7

        &OUTER_SCF

        MAX_SCF 5

        EPS_SCF 1.0E-7

        &END

    &END SCF

    &XC

      &XC_FUNCTIONAL PBE

      &END XC_FUNCTIONAL

        &XC_GRID

                XC_SMOOTH_RHO NN50

                XC_DERIV NN50_SMOOTH

        &END XC_GRID

    &END XC

&END DFT

...

I've also tried it with no specification of filename or each or common iteration levels, also for nonperiodic case with MT poisson solver but I never get any file or part of the output mentioning dipole or wannier centres. Quite sure the mistake is something really stupid, but I've been just spending few nights on it and still cannot figure it out. 

Any help would be much appreciated!

J.

[Jana]

(just noticed few typos - 
ADD_LAST NUMERIC and  REFERENCE COAC)

[JQ]

Hi Jana,

I have just done a test run on my pc based on your input. Your input seems working fine that I manage to get the output of delta dipole moment and etc, saved into the files as defined. You may refer to the attached input file and output file (only few MD steps), for your reference. I am using CP2K 2.3 and you can find its details in the output file

JQ

[Wagner Homsi Brandeburgo]

Dear Jana, Jing,

probably by now you have already solved the problem, but I was just faced with the same

issue and I've just figured out what happened. Apparently, there was a minor change from 2.3, 2.4 (development version) and 2.4 (trunk version), my guess is that you're using (2.4 trunk). On this version the location of the subsections related to printing dipole moments and wannier centers have changed on the input file. Now, you don't need the LOCALIZATION section anymore, you can just start the subsection TOTAL_DIPOLE inside LOCALIZE%PRINT. 

In your case, just delete the following lines:

 &LOCALIZATION

and

&END (refering to LOCALIZATION)

and move &END LOCALIZE to after &END PRINT

cheers,

Wagner.

ps. if you keep the old sintax the code won't complaint, it'll just run normally without computing it, maybe it's something for the developers to fix.

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[Jana]

Dear Wagner,

it is sorted, thanks for the remark though.

I am a bit puzzled by the post-processing - give time difference in input file (in atomic units):

 [CAUTION: this is the MD time step times the sampling frequency.]

The sample value in the fourier transform utility was 17. My time step is 0.5 fs but how do I find out what the sampling frequency is? I understand I should find out after how many samples I save one, but how do I get that?

Originally I used the Used time column in *ener file but JQ found out it wasn't it.

[Sandeep Kumar Reddy]

Hi,

     It should be calculated as follows. 

timestep*dumping_frequency

timestep = 0.5 fs =  20.665 a. u. 

dump_frequency = how often are you calculating the dipole moment and dumping it to the output file. From your input file, i believe it is 1. 

so sampling frequency =  20.665*1 = 20.665   

Hope this helps.

Regards,

Sandeep

PS: You need not calculate dipole moment of the system at every MD step. To save CPU time, you can calculate dipole moment at every 5th MD step.  In this case, the sampling frequency is 103.325 (20.665*5).