<div>Thank you , Young-Su.</div>
<div><span class="gmail_quote">2006/11/10, Young-Su Lee <<a href="mailto:email@example.com">firstname.lastname@example.org</a>>:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Dear Janiet,<br><br>><br>> I have several questions about distentangle process giving in SMV<br>> paper.
<br>> We should set an energy window for distentangle process , while my<br>> question<br>> is about this energy window's setting. Should all bands in the energy<br>> window<br>> be included in the distentangle process ?
<br><br>You can exclude certain bands: that's one of the features in wannier90.</blockquote>
<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 ?
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">> Just count bands in this window , and make<br>> sure there are several bands above this window ?<br>
<br>I think that will work.<br><br>><br>> Another question is about wannierise process for metal cnt. I just<br>> wanna<br>> repeat yongsu's work on pristine cnt , and obtain the minimal basis<br>> for cnt.
<br>> But there are some problems i donot understand clearly. Just with<br>> occupied<br>> bands for wannierise, there is no problem both fo semi/metal cnt to reach<br>> convergence. One of my confusion is why could wannierise reach
<br>> convergence without distentangle process in metal cnt since i just set<br>> 'num_wan' to the number of valence bands ?<br><br>CNT is a zero gap semicondutor and below the Fermi level, the number of<br>bands is the same regardless of a k-vector you choose.
<br><br>However, for a truly metallic system you will never(?) find this<br>situation, e.g.<br>in SMV paper, number of bands below E_F varies when you sweep through<br>the k-space:so there is no hope of getting WFs without disentanglement.
<br><br>For CNT, with a bit of fortune, you can still have localized WFs without<br>disentanglement.<br><br>Here are two things:<br><br>First of all, it's not always the case. I once tried (5,0), but it<br>didn't work.<br>
<br>Second, those WFs are not good for band structure interpolation.<br>If you do band structure interpolation with those WFs, you will find an<br>extremely poor agreement<br>with one you get from PWSCF code, except the k-points you sampled to get
<br>WFs.<br><br>In a word, you can get WFs from valence band only, but they are useless<br>(well, it also depends on what you want to do with them).<br><br><br>> What we need to consider<br>> is the degenerate bands in distentangle process , is it right ?
<br><br>This question is not clear enough for me.</blockquote>
<div>Sorry for my expression. </div>
<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 ?
<div>> Next i<br>> consider '2.5 orbitals per atom' to distentangle WFs. Just with exact<br>> 'nat<br>> X 2.5' bands for 'nscf' calculation , it is difficult to reach<br>> convergence<br>> in wannierise process ,
<br>> Does this problem relate to 'not all bands inculded in the energy<br>> window ' ?<br>><br>It depends on many sorts of things.<br>First, you have to plot your band structure from nscf calculation before<br>conducting any Wannier-related calculations.
<br>Make sure that your 'nbnd' is big enough to cover whole<br>bonding+antibonding pi-bands.<br>If you've done this step, I don't know the answer without looking at the<br>output files.<br> </div>
<div>a poor question is about antibonding pi bands counting ,</div>
<div>Does it equal to the number of atoms ?</div>
<div>I appreciate your kind reply.</div>