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Multiplicity

satish
2015-01-05
2015-01-05
  • satish

    satish - 2015-01-05

    Hello

    I was trying to calculate the atomic energies of O,H etc. By default (using z-spin) I suppose the unpaired electron is assumed to be a doublet. However, I want to find ground state energy of triplet O atom. How do I set a triplet multiplicity?

    Thanks.

     
  • Ravishankar Sundararaman

    Actually, the default multiplicity is always singlet, regardless of number of electrons. (Standard behaviour for solid state codes, because odd number of electrons per unit cell does not mean spin polarized.)

    You can control the multiplicity using the elec-initial-charge command. In spin polarized mode, you can adjust the charge of each spin channel. So to create a neutral doublet, you would do:

    elec-initial-charge +0.5 -0.5
    

    and for a neutral triplet, you would do:

    elec-initial-charge +1 -1
    

    If you want to create a charged spin-polarized system, you reference the net electron count in each spin channel to the neutral unpolarized case. Therefore, for a doublet anion, you would do

    elec-initial-charge +1 0
    

    Note that the units are in electrons, not conventional charge i.e. eleectron-is-positive charge convention.

    See the documentation of command elec-initial-charge for syntax details

    Cheers,
    Shankar