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<div class="moz-cite-prefix">dear Jiqiang Li,<br>
the VBM is probably degenerate and depending of minute details
(like the smearing) which state comes last can be randomly
assigned.<br>
It would make more sense to compute some density of state
related quantity adding contribution from all states (weighted
with<br>
a smeared delta-function) \sum_i
\delta(e_i-e_VBM)|<f|dVtot/dR|i>|^2 / \sum_i
\delta(e_i-e_VBM).<br>
i think this should be more stable.<br>
<br>
there are options in the pp.x tool to plot a single wavefunction
or the locally density of states at the Fermi energy. This could
be easily modified to compute ldos(e_VBM) as a function of e_VBM
as a parameter. And you could see if the problem is related to
degeneracy.<br>
<br>
regards,<br>
stefano<br>
<br>
On 20/09/2015 04:29, Jiqiang Li wrote:<br>
</div>
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<div><span></span>Dear Stefano,</div>
<div> The system is a semiconductor, but it is +1 charged.
Pwscf forces me to set a value for degauss. I want to evaluate
the <f|dVtot/dR|i>, where the |i> and |f> refer to
the wavefunctions of valence band maximum (VBM) and the isolated
state <span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;">induced by defect in the band gap,
respectively. I found that the related wavefucntions change a
lot when the weights (occupations) of the highest bands
change. By the way, I am performing a Gamma point only
calculation for a large supercell with a lattice constant
exceeding 10 Angstrom.</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;"> I believe the many
quantities (such as total energy) do not change significantly
when the occupations of highest states vary, because
contribution from these states is relatively small than that
from the rest states. So I am wondering whether it is normal
that wavefunctions of highest occupied states change
remarkably when the occupations of highest states vary.</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;"><br>
</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;">Best regards!</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;">Jiqiang</span></div>
<div><br>
</div>
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<div><b>From:</b> <a moz-do-not-send="true"
href="mailto:degironc@sissa.it">stefano de gironcoli</a></div>
<div><b>Date:</b> 2015-09-20 04:07</div>
<div><b>To:</b> <a moz-do-not-send="true"
href="mailto:q-e-developers@qe-forge.org">q-e-developers</a></div>
<div><b>Subject:</b> Re: [Q-e-developers] smearing style</div>
</div>
</div>
<div>
<div class="FoxDiv20150920100536182427">
<div class="moz-cite-prefix">Dear Jiqianq<br>
the answer to your question depends on which physical
quantity you want to calculate.<br>
Is the state you want to study spatially localized ? is
it an isolated (narrow band) in a band energy gap ? are
you interested in the shallow donor states formed by the
holes at the bottom of the conduction band of a doped
semiconductor ? Or is your system a metal ?<br>
clarifying to yourself what is the question you want to
answer will help you to figure out how to compute a
physically meaningful number. <br>
<br>
stefano<br>
<br>
On 19/09/2015 12:37, Jiqiang Li wrote:<br>
</div>
<blockquote cite="mid:2015091918362124730618@fudan.edu.cn"
type="cite" style="margin-top: 0px; margin-bottom: 0px;
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<div><span></span>Dear <span style="font-size: 10.5pt;
line-height: 1.5; background-color: window;">Lorenzo,</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;"> For example, for a
supercell with 100 electrons, it will be of 99
electrons when the system is +1 charged. I consider
the 50th band as the highest occupied band with half
occupation.</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;"><br>
</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;">Jiqiang</span></div>
<div><br>
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PADDING-TOP: 8px">
<div><b>From:</b> <a moz-do-not-send="true"
href="mailto:paulatz@gmail.com">Lorenzo Paulatto</a></div>
<div><b>Date:</b> 2015-09-19 18:14</div>
<div><b>To:</b> <a moz-do-not-send="true"
href="mailto:q-e-developers@qe-forge.org">General
discussion list for Quantum ESPRESSO developers</a></div>
<div><b>Subject:</b> Re: [Q-e-developers] smearing
style</div>
</div>
</div>
<div>
<div>Dear Jiqiang,</div>
<div>the "highest occupied banda" are obviously
defined only for insulators, i.e. </div>
<div>there is no such thing as a highest occupied
bands when using a smearing, what </div>
<div>threshold do you use for occupied/non occupied? </div>
<div> </div>
<div>kind regards </div>
<div> </div>
<div>On Saturday, September 19, 2015 05:48:09 PM
Jiqiang Li wrote:</div>
<div>> Dear developers,</div>
<div>> I want to use the wavefunctions of
highest occupied bands in a</div>
<div>> charged system to evaluate some quantities,
such as psi_i(r) ＊psi_j(r) .</div>
<div>> However, I found that the wavefunction
sensitively depends on the degauss</div>
<div>> value. So, how to choose a suitable value
for degauss when I want to</div>
<div>> obatain a physically meaningful quantity.</div>
<div> </div>
<div>> </div>
<div>> Best regards!</div>
<div>> Jiqiang Li</div>
<div>> </div>
<div>> </div>
<div>> </div>
<div> </div>
<div>-- </div>
<div>Lorenzo Paulatto - Paris</div>
<div> </div>
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