Help for 2nd order CPMD

[DMITRII Drugov]

Dear CP2k community,

I am trying to run the 2nd order CPMD. I have ionic liquid system in NVT ensemble. 

Could you please advice how to select GAMMA and NOISY_GAMMA?

Also in this section below.

&MOTION

  &MD

    ENSEMBLE LANGEVIN

    ...

    &LANGEVIN

      GAMMA 0.001

    &END LANGEVIN

    ...

  &END MD

I have my BOMD script below.

Many thanks,

Dmitrii

&FORCE_EVAL

  METHOD QS

  &DFT

    BASIS_SET_FILE_NAME BASIS_MOLOPT

    POTENTIAL_FILE_NAME GTH_POTENTIALS

    CHARGE 0

    MULTIPLICITY 1

    &MGRID

      CUTOFF 400

      NGRIDS 4

      REL_CUTOFF 40

    &END MGRID

    &QS

       METHOD GAPW

       EPS_DEFAULT 1.0E-12

       EXTRAPOLATION ASPC

       EXTRAPOLATION_ORDER 3

    &END

    &SCF

      SCF_GUESS ATOMIC

      EPS_SCF 1.0E-6

      MAX_SCF 15

      &OT

       MINIMIZER DIIS

       PRECONDITIONER FULL_KINETIC

       &END OT

      &OUTER_SCF

       EPS_SCF 1.0E-6

       MAX_SCF 20

      &END

      &PRINT

       &RESTART

        &EACH

         MD 0

        &END EACH

       &END

      &END

    &END SCF

   

    &XC

      &XC_FUNCTIONAL BLYP

      &END XC_FUNCTIONAL

      &XC_GRID

       XC_DERIV NN10_SMOOTH

       XC_SMOOTH_RHO NN10

      &END XC_GRID

      &vdW_POTENTIAL

        DISPERSION_FUNCTIONAL PAIR_POTENTIAL

         &PAIR_POTENTIAL

            PARAMETER_FILE_NAME dftd3.dat

               TYPE DFTD3

               REFERENCE_FUNCTIONAL BLYP

        &END PAIR_POTENTIAL

     &END vdW_POTENTIAL

    &END XC

    &POISSON

      PERIODIC xyz

      POISSON_SOLVER PERIODIC

    &END POISSON

  &END DFT

  &SUBSYS

    &CELL

      ABC 19.3457 19.3457 19.3457

      PERIODIC xyz

    &END CELL

    &TOPOLOGY

      COORD_FILE_NAME npt.xyz

      COORD_FILE_FORMAT XYZ

    &END TOPOLOGY

    &KIND H                              

      BASIS_SET TZV2P-MOLOPT-GTH

      POTENTIAL GTH-BLYP-q1            

    &END KIND

    &KIND Al

      BASIS_SET DZVP-MOLOPT-SR-GTH

      POTENTIAL GTH-BLYP-q3

    &END KIND

    &KIND F

      BASIS_SET TZVP-MOLOPT-GTH

      POTENTIAL GTH-BLYP-q7

    &END KIND

    &KIND O

      BASIS_SET TZVP-MOLOPT-GTH

      POTENTIAL GTH-BLYP-q6

    &END KIND

    &KIND C

      BASIS_SET TZVP-MOLOPT-GTH

      POTENTIAL GTH-BLYP-q4

    &END KIND

    &KIND S

      BASIS_SET TZVP-MOLOPT-GTH

      POTENTIAL GTH-BLYP-q6

    &END KIND

    &KIND N

      BASIS_SET TZVP-MOLOPT-GTH

      POTENTIAL GTH-BLYP-q5

    &END KIND

   &END SUBSYS

&END FORCE_EVAL

&GLOBAL

  PROJECT IL_nvt

  RUN_TYPE MD

  PRINT_LEVEL LOW

  FFTW_PLAN_TYPE EXHAUSTIVE

&END GLOBAL

&MOTION

 &MD

  ENSEMBLE NVT

  STEPS 2000

  TIMESTEP 0.5

  &THERMOSTAT

   TYPE NOSE

   REGION MASSIVE

   &NOSE

    TIMECON 10.00

   &END NOSE

  &END THERMOSTAT

  TEMPERATURE 303

 &END MD

  &PRINT

   &TRAJECTORY

     &EACH

       MD 1

     &END EACH

   &END TRAJECTORY

   &VELOCITIES OFF

   &END VELOCITIES

   &FORCES OFF

   &END FORCES

   &RESTART_HISTORY

     &EACH

       MD 500

     &END EACH

   &END RESTART_HISTORY

   &RESTART

     BACKUP_COPIES 3

     &EACH

       MD 1

     &END EACH

   &END RESTART

  &END PRINT

&END

&EXT_RESTART

  RESTART_FILE_NAME nvt-1.restart

&END

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[Marcella Iannuzzi]

Dear Dmitrii

The parameters are determined by testing. 

One has to find the conditions for which the  noise term generates the correct average temperature, as measured by the equipartition theorem.

This leads to the correct sampling. 

Gamma should be small, as long as the error in the forces is small. Under these conditions the dynamical properties are  correct.   

The first term of comparison to determine the accuracy of the SGCP description is obtained from the deviations in  energy  and  forces  with  respect  to  the  BO  values  at the same coordinates.

The force deviation has to have a vanishing average, and also that the distribution of errors should be Gaussian.

Regards

Marcella

[DMITRII Drugov]

Dear Marcella,

Thank you for this information.

Let's see how it goes.

I will keep you posted if something comes up.

Kind regards,

Dmitrii

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[Moon Moon]

Dear lannuzzi

Thank you for careful comments on SGCP settings.

As you said, the accuracy of the SGCP should be determined by comparing with BO values at the same coordinates.

But even among BO simulations with different parameters, the lines of energy and forces may change.

So how can I compare SGCP values with BO values ?

Moon

[Marcella Iannuzzi]

Dear Moon

this is not true, obviously we are talking of same computational settings, as basis sets, cutoff, pseudo potential etc. 

In this case the forces should be the same but for the sgcp deviation, which anyway should be normally distributed.

Kind regards

Marcella