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

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The forum discussion centers on the analysis of bonding characteristics in ultrathin ZnO nanowires under uniaxial compression, as detailed in the paper "Direct to indirect band gap transition in ultrathin ZnO nanowires under uniaxial compression" published in APPLIED PHYSICS LETTERS. The author highlights that the highest occupied molecular orbital (HOMO) bonding at the Gamma-point is primarily influenced by the O pz and Zn dz2 states. The discussion also addresses confusion regarding the equivalence of p and d sub-orbitals and emphasizes that computational tools like SIESTA can provide insights into orbital contributions during bonding analysis.

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zhaohs
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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.

Regards.
 
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zhaohs said:
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.

Regards.

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.
 
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