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<div>Does it mean that we could do distentangle process in certain
energy window with as minimal bands as possible ? I think the bands
exclude of coz affect results, what we should take care is that the
bands of same characteristics should not be excluded . Is it right for
my understanding this exclude feature ? <br>
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I would start from including all bands and check projection
information of disentangled subspace to the original space.<br>
If certain bands have very very small contribution, you may exclude
these bands. I'm not totally sure whether it's going to work.<br>
In my opinion, exclude feature will be useful when some bands are
hampering disentanglement/minimization procedure <br>
while you are sure that they should not be included in the disentangled
subspce by symmetry.<br>
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<div>To my knowledge, besides bandgap, the difference between
insulator/semiconductor and metal is fermi surface effect in metal
systems. there are entangled bands near fermi surface in metal
systems. So for distentangle process , it is not due to fermi surface
effect , but to bands degenerate . Is it right for my understanding ?
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I think disentanglement will be useful when gap is small even if the
system is not metallica.<br>
Suppose the system has very very small gap at Gamma (G afterwards). <br>
Then it is likely that HOMO(G+delta) has a character of LUMO(G).<br>
In that case, by including LUMO(G) in the disentangled subspace, we can
better describe HOMO(G+delta).<br>
I may not the right person to explain this, but this is the best answer
I can give.<br>
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<div>a poor question is about antibonding pi bands counting ,</div>
<div>Does it equal to the number of atoms ?</div>
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Yes. But nbnd must be set higher than 2.5*nat, since sp2 anti-bonding
or free electron-like states mix with anti-bonding pi-bands.<br>
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