Charge calculation -- Charged system

[Sandeep Kumar Reddy]

Dear All,

                 I am trying to calculate atomic charges of a system whose total charge is +1. I am not able to get charges correctly as expected. 

For the sake of better understanding, i have taken an easy system which consists of 1 water molecule and 1 H atom (Total 4 atoms). 

First, I used Gaussian software to calculate the atomic charges on this system. 

 Mulliken atomic charges: (Method:  hf 6-31g(d))

              1

     1  O   -0.857873

     2  H    0.424054

     3  H    0.433819

     4  H    1.000000

 Sum of Mulliken atomic charges =   1.00000

Using CP2K, i have got the following charges. 

MULLIKEN POPULATION ANALYSIS

 #  Atom  Element  Kind  Atomic population                Net charge

       1     O        1          5.956324                  0.043676

       2     H        2          0.814162                  0.185838

       3     H        2          0.809985                  0.190015

       4     H        2          0.419529                  0.580471

 # Total charge                  8.000000                  1.000000

In case of atom centered basis set, i can clearly see +1 charge is localized on 1 H atom where as it is not the case using mixed basis set. Could anybody help me in this regard? The cp2k input file is enclosed. 

Thanks.

Regards,

Sandeep 

[Ari Paavo Seitsonen]

Dear Sandeep,

  Do I see correctly that with GaussianXX-software you used the Hartree-Fock method, with CP2K PBE-GGA? Could that lead to a certain difference, probably yielding a different level of localisation of the wave functions?

    Greetings from Rome,

       apsi

2014/1/21 Sandeep Kumar Reddy <kuma...@gmail.com>

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  Ari P Seitsonen / Ari.P.S...@iki.fi / http://www.iki.fi/~apsi/
  Physikalisch-Chemisches Institut der Universität Zürich
  Tel: +41 44 63 55 44 97  /  Mobile: +41 79 71 90 935

[hut...@chem.uzh.ch]

Hi

you are calculating a water molecule with a distant proton.
GGA functionals are known to get this wrong. They fail to
localize the charge and give a 'smeared' charge distribution.
See the 0.5 charge on the lone H.
HF on the other hand localizes the charge, as you can see in
your Gaussian calculation.

regards

Juerg Hutter

--------------------------------------------------------------
Juerg Hutter Phone : ++41 44 635 4491
Institut für Chemie FAX : ++41 44 635 6838
Universität Zürich E-mail: hut...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
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To: cp...@googlegroups.com
From: Sandeep Kumar Reddy
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Date: 01/21/2014 06:55AM
Subject: [CP2K:4905] Charge calculation -- Charged system

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[attachment "cp2k.inp" removed by Jürg Hutter/at/UZH]

[Sandeep Kumar Reddy]

Dear Apsi and Hutter,

                                         Thank you for the reply. Yes, your guess is correct. I used HF method in Gaussian09 software. I repeated the charge calculation with DFT method, and as you said, i got the similar charges as that i found using cp2k software. 

My purpose of these test runs is study "the proton irradiation of a surface". If the charge on the proton is not +1, then is it correct to assume it as a proton as when it approaches the surface, there will be a transfer of charge between proton and the surface. Kindly let me know if this is wrong.

Thanks.

Regards,
Sandeep 

[hut...@chem.uzh.ch]

Hi

with any standard GGA you will get "charge transfer" at any
distance of the proton. The result will be un-physical.

regards

Juerg Hutter

--------------------------------------------------------------
Juerg Hutter Phone : ++41 44 635 4491
Institut für Chemie FAX : ++41 44 635 6838
Universität Zürich E-mail: hut...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
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-----cp...@googlegroups.com wrote: -----
To: cp...@googlegroups.com
From: Sandeep Kumar Reddy
Sent by: cp...@googlegroups.com

Date: 01/21/2014 09:45AM
Subject: Re: [CP2K:4909] Charge calculation -- Charged system