Getting wrong Mulliken charges for thiols on gold surface system

[Vikash Khokhar]

Hi CP2K community,

I'm optimizing Au (111) 5 layers surface with aromatic thiols on the surface. 

But the charge on S atoms is +ve, and the first and last layers of Au have -ve charge.

But S atoms should have +ve charge. 

Please suggest how I can get the correct charges.

I have attached the Mulliken charges file and the coordinates file here, just in case you'd like to have a look.

The input file is -

--------------------------------------------------------------------------------------------------------------------------------------------

&GLOBAL

  PROJECT Au_2DMBT_tilt
  RUN_TYPE GEO_OPT
  PRINT_LEVEL MEDIUM
&END GLOBAL

&MOTION
  &GEO_OPT
    TYPE MINIMIZATION
    OPTIMIZER BFGS
    MAX_DR    3.00E-03
    MAX_FORCE 4.50E-04
    RMS_DR    1.50E-03    
    RMS_FORCE 3.00E-04
    MAX_ITER 3000
  &END GEO_OPT

  &CONSTRAINT
    &FIXED_ATOMS
      COMPONENTS_TO_FIX XYZ
      LIST 1..48
    &END FIXED_ATOMS
  &END CONSTRAINT

&END MOTION  

&FORCE_EVAL
  METHOD QS

  &DFT
    BASIS_SET_FILE_NAME /home/spremkumar.iitm/vikash/cp2k_pot/BASIS_MOLOPT
    POTENTIAL_FILE_NAME /home/spremkumar.iitm/vikash/cp2k_pot/GTH_POTENTIALS

    &QS
      METHOD GPW
      EXTRAPOLATION USE_GUESS
      EPS_DEFAULT 1.0E-10
    &END QS

    &MGRID
      CUTOFF 500
      NGRIDS 4
      REL_CUTOFF 60
    &END MGRID

    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-05
      MAX_SCF 200
      ADDED_MOS 10

      &DIAGONALIZATION T
        ALGORITHM STANDARD
      &END DIAGONALIZATION
     
      &SMEAR ON
        METHOD FERMI_DIRAC
        ELECTRONIC_TEMPERATURE [K] 300
      &END SMEAR

      &MIXING T
        METHOD BROYDEN_MIXING
        ALPHA 0.4
        NBROYDEN 8
      &END MIXING
    &END SCF

    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL

      &vdW_POTENTIAL
        DISPERSION_FUNCTIONAL PAIR_POTENTIAL
        &PAIR_POTENTIAL
            PARAMETER_FILE_NAME /home/spremkumar.iitm/vikash/cp2k_pot/dftd3.dat
            TYPE DFTD3
            REFERENCE_FUNCTIONAL PBE
            R_CUTOFF 25.0
        &END PAIR_POTENTIAL
     &END vdW_POTENTIAL
    &END XC

    &KPOINTS
      SCHEME MONKHORST-PACK 2 3 1
      FULL_GRID .TRUE.
      PARALLEL_GROUP_SIZE  0
    &END KPOINTS

  &END DFT

  &SUBSYS
    &CELL
      PERIODIC XYZ
      A    17.3099747000000015    0.0000000000000000    0.0000000000000000
      B     0.0000000000000000    9.9939184000000001    0.0000000000000000
      C     0.0000000000000000    0.0000000000000000   35.0000000000000000
    &END CELL

    &COORD
      @INCLUDE Au_2DMBT_tilt.xyz
    &END COORD

    &KIND Ag
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE
    &END KIND
    &KIND Au
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE
    &END KIND
    &KIND H
      BASIS_SET DZVP-MOLOPT-GTH
      POTENTIAL GTH-PBE
    &END KIND
    &KIND C
      BASIS_SET DZVP-MOLOPT-GTH
      POTENTIAL GTH-PBE
    &END KIND
    &KIND S
      BASIS_SET DZVP-MOLOPT-GTH
      POTENTIAL GTH-PBE
    &END KIND

  &END SUBSYS

--------------------------------------------------------------------------------------------------------------------------------------------

Thank you

Vikash Khokhar

Project Assistant

Pradeep research group, 

DST Unit of Nanoscience & Thematic Unit of Excellence, 

Department of Chemistry

Indian Institute of Technology Madras, Chennai, India

Web: pradeepresearch.org 

[Vikash Khokhar]

Sorry for the mistake. 
I mentioned, 'But S atoms should have +ve charge,' but it was 'S atoms should have -ve charge.'

[Vikash Khokhar]

Anybody please answer this question?

[Victor Volkov]

Good day, Vikash.

According to my knowledge and experience,

classification "wrong Mulliken"

does not sound right.

The Mulliken protocol is as described in literature.

There are many publications to report when it was very helpful and 

when it did not bring numbers consistent with the experimental.

The approach by Robert Mulliken (I graduated from the lab which stemmed from his)

was discussed to contradict experimental anticipations when in systems with metals.

You have to explore literature on your own.

This does not mean that it would compute "wrong Mulliken".

There are other protocols with own benefits and lacks.

In general, computing one set of charges for a system does not have a strong value.

Instead, comparing how charges would change when you explore various relevant

systems using the same level of theory may be scientific.

You may try RESP as a complimentary approach.

Perhaps, the developers and other users would be kind enough

to update this reply if I made a mistake.

Victor

  &PROPERTIES
    &RESP
    USE_REPEAT_METHOD
    &SPHERE_SAMPLING
     AUTO_VDW_RADII_TABLE UFF
     AUTO_RMIN_SCALE 1.0
     AUTO_RMAX_SCALE 10
    &END
      &PRINT
&RESP_CHARGES_TO_FILE
          FILENAME resp.dat
            &EACH
            MD 1
            &END EACH
&END RESP_CHARGES_TO_FILE
      &END PRINT  
    &END RESP
    &FIT_CHARGE
    &END FIT_CHARGE
  &END PROPERTIES
&END FORCE_EVAL

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[Vikash Khokhar]

Thanks, Victor, for your kind reply and suggestions.

My apologies for mentioning the 'wrong Mulliken charges.' I just wanted to know why I was getting unreasonable charges for my system, was I missing something.

I'll try your suggestions and will get back to you.

Please let me know if I'm missing something in my calculations to compute reasonable charges for the metallic systems!

Thank you

Vikash