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Mulliken Population when using double zeta basis

  1. Jul 25, 2005 #1
    Is there anyone who can help me?

    I was bothered by the negative occupation in atomic orbital like 5p here.
    I don't understand what it means. By the way, 6.00 here is the total number of charges.

    # 5s 5s 5py 5pz 5px 5py 5pz 5px 4dxy 4dyz 4dz2 4dxz 4dx2-y2 4dxy 4dyz 4dz2 4dxz 4dx2-y2
    6.000 0.206 0.751 -0.784 -0.784 -0.784 0.788 0.788 0.788 0.981 0.981 1.011 0.981 1.011 0.087 0.087 -0.098 0.087 -0.098

    Thank you!
    Last edited: Jul 25, 2005
  2. jcsd
  3. Jul 25, 2005 #2


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    I know very little about Mulliken Pop Analysis, but I do remember that interpreting the DS (I'm not sure if this is the standard convention, but I'm talking about the product of the density matrix, D, and the overlap matrix, S) matrix elements as atomic orbital occupation values is "problematic". One of the reasons is what you've pointed out (negative occupations), and the other is that sometimes you get occupation numbers greater than 2 for an orbital.

    I have no clue what one does about this.

    You may find something here : Gordon M. S., Schmidt, M. W., Chaban, G. M., Glaesemann, K. R., Stevens, W. J. & Gonzalez, C. (1999) J. Chem. Phys. 110, 4199-4207.
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