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Bonding analysis at HOMO, could you please give me some hints.

  1. Jun 18, 2011 #1
    Hi all,

    Currently, I'm reading the paper: Direct to indirect band gap transition in ultrathin ZnO nanowires under uniaxial compression [APPLIED PHYSICS LETTERS 94, 113114, 2009].

    You can download this paper from the following url:

    http://h1.ripway.com/zhaohs/Direct ...ansition in ultrathin ZnO nanowires under.pdf

    At the top of page 3, the author said:

    A detailed analysis on the characteristics of atomic orbital contribution of the
    highest occupied molecular orbital (HOMO) shows that
    bonding at Gamma-point is mainly contributed from the O pz and
    Zn dz2 states, with equal components from all the six Zn and
    O in the supercell. For point E and F in Fig. 4, the key
    bonding characteristics are also the O pz and Zn dz2, but from
    only two (L=0.48 nm) or four (L=0.47 nm) Zn and O atoms.
    The analyses indicate that bonding of HOMO at
    Gamma-point is much stronger than that at E or F point. Therefore,
    during uniaxial compression, the energy lowering at Gamma-point
    will be much faster than that at E or F point.

    But I cann't figure out what calculations should I performed in order to obtain the above information within siesta.

    Furthermore, the author said that the bonding are mainly contributed from O pz and Zn dz2. But in my mind, all of the three sub-orbitals of p (px,py, pz) are exactly equivalent, and that is also the case for the five sub-orbitals of d (dz2, dxz, dxy, dx2-y2, dyz). So, how should they know the bonding are mainly contributed from O pz and Zn dz2?

    Could you please give me some hints? Thanks in advance.

    Last edited by a moderator: Apr 26, 2017
  2. jcsd
  3. Jun 19, 2011 #2


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    Science Advisor

    Well, I don't know what siesta is .. I guess it's some sort of solid-state computational physics package .. so I'm afraid I can't be much help there.

    However, I can perhaps help with your confusion about the spatial orbitals. The spatial orbitals (i.e. px, py, pz, or the 5 d-orbitals) are only "equivalent" (I assume you meant degenerate), when an atom is in isotropic space. In this case, the atoms are participating in a covalent bonding network, and thus are most definitely NOT in isotropic space. As to how the authors know specifically that it is the pz and dz[sup2[/sup] orbitals contributing .. that is one of the things you can keep track of with a computational quantum electronic structure package.
    Last edited by a moderator: Apr 26, 2017
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