<div dir="ltr"><font face="arial, helvetica, sans-serif"><span style="font-size:12.8px;color:rgb(0,0,0);line-height:18.2px">Dear </span><span style="font-size:12.8px;color:rgb(0,0,0);line-height:18.2px"><b>Prof. Paolo, </b></span><span style="font-size:12.8px;color:rgb(0,0,0);line-height:18.2px"><span style="color:rgb(34,34,34);font-size:12.8px;font-weight:bold;white-space:nowrap">Giuseppe</span><b>, </b></span></font><span style="font-size:12.8px;font-weight:bold;white-space:nowrap">ashkan </span><font face="arial, helvetica, sans-serif"><span style="font-size:12.8px;color:rgb(0,0,0);line-height:18.2px">Thank you for your valuable suggestions.</span></font><div><font color="#000000" face="arial, helvetica, sans-serif"><span style="font-size:12.8px"><br></span></font></div><div><font face="arial, helvetica, sans-serif"><span style="font-size:12.8px">After analyzing the structure I think the whole mess is done by surface dangling bonds.Here I don't want to saturate the surface as I have interested to simulate the excitonic and optical properties of the bear clusters.</span><span style="font-size:12.8px"> </span></font></div><div><br></div><div><font face="arial, helvetica, sans-serif"><span style="font-size:12.8px"><br></span></font></div><div><font face="arial, helvetica, sans-serif"><span style="font-size:12.8px"><br></span></font></div><div><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><span style="font-family:"times new roman",serif">Best regards,</span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><span style="font-family:"times new roman",serif">Naren</span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><span style="font-family:"times new roman",serif"> </span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><span style="font-family:"times new roman",serif"> </span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><span style="font-family:"times new roman",serif"> </span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">Dr. Narendra Nath Ghosh</span></b><span style="font-family:"times new roman",serif"></span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">Research Associate</span></b><span style="font-family:"times new roman",serif"></span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">University of Gour Banga</span></b></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">Department of Chemistry</span></b><span style="font-family:"times new roman",serif"></span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">Malda-732102</span></b><span style="font-family:"times new roman",serif"></span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">India</span></b><span style="font-family:"times new roman",serif"></span></p><p class="MsoNormal" style="margin-bottom:0.0001pt;font-size:12.8px;line-height:normal;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial"><b><span style="font-family:"times new roman",serif">Phone: +919126667601</span></b></p></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font></div><div><font color="#000000" face="times new roman, serif"><span style="font-size:12.8px"><br></span></font><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Apr 21, 2017 at 9:45 AM, Giuseppe Mattioli <span dir="ltr"><<a href="mailto:giuseppe.mattioli@ism.cnr.it" target="_blank">giuseppe.mattioli@ism.cnr.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-"><br>
> Use more intense kpoint mesh.<br>
<br>
</span>No, this is useless. 0D systems have molecular-like flat rather than dispersed energy levels in the reciprocal space. There is no reason to sample the<br>
Brillouin zone with more k-points.<br>
<br>
HTH<br>
Giuseppe<br>
<div><div class="gmail-h5"><br>
On Friday, April 21, 2017 05:06:42 PM ashkan shekaari wrote:<br>
> Dear Naren,<br>
> Increase ecut. Use more intense kpoint mesh.<br>
><br>
> On Apr 21, 2017 4:50 PM, "Giuseppe Mattioli" <<a href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>><br>
><br>
> wrote:<br>
> > Dear Naren<br>
> > Your calculation is very expensive, and calculations of 0D objects in a<br>
> > plane-wave/PBC framework are often prone to convergence issues. This said,<br>
> > you<br>
> > can try to<br>
> ><br>
> > 1) perform a simple calculation of the PbSe unit cell with the same<br>
> > pseudopotentials. Are there similar convergence problems? You are using hgh<br>
> > that<br>
> > are norm-conserving pseudopotentials (NCPP) and they could require a<br>
> > richer pw basis set. I would not be surprised if, after proper convergence<br>
> > tests<br>
> > performed on the unit cell, you ended up with ecutwfc=70~80 Ry. There is<br>
> > no need to specify ecutrho, anyway. It is fixed to a default ecutwfc*4 value<br>
> > in the case of NCPP.<br>
> ><br>
> > 2) lower mixing_beta, even down to very small values such as 0.05~0.01.<br>
> > Sometimes it helps to reach convergence (slowly but steady).<br>
> ><br>
> > It is impossible to say more without looking at you cluster, but if it is<br>
> > simply cut out from the bulk along low-index directions (e.g., a cube) you<br>
> > have to deal with a mess of surface dangling bonds that want to play nasty<br>
> > charge displacements between occupied and unoccupied electronic levels,<br>
> > even inducing a metallic character in your cluster. People used to<br>
> > saturate such dangling bonds with pseudo-H atoms (H atoms having formal<br>
> > charge<br>
> > lower or higher than 1.0, depending on the formal valence of the saturated<br>
> > atom). If you don't want to saturate the surface you must keep into account<br>
> > the possibility that the cluster surface reconstruct, and you should<br>
> > anticipate reconstruction trends by lplacing the atoms nearer to the<br>
> > expected<br>
> > final positions. It could be a very difficult task, look at the<br>
> > instructive story of the Si 7x7 reconstruction in this movie!<br>
> ><br>
> > <a href="https://www.youtube.com/watch?v=BXdC0NhAMBY" rel="noreferrer" target="_blank">https://www.youtube.com/watch?<wbr>v=BXdC0NhAMBY</a><br>
> ><br>
> > HTH<br>
> > Giuseppe<br>
> ><br>
> > On Friday, April 21, 2017 04:06:06 AM Narendranath Ghosh wrote:<br>
> > > Dear all!<br>
> > ><br>
> > ><br>
> > ><br>
> > > I am currently trying to optimizing a Pb180Se180 cluster using QE.<br>
> > ><br>
</div></div>> > > But after 83 iterations it didn’t get converged.<br>
<div><div class="gmail-h5">> > ><br>
> > > *Input *<br>
> > ><br>
> > > calculation='relax',<br>
> > ><br>
> > > outdir='/staging/op/NAREN_USC/<wbr>PbSe_360_FINAL_based_Pb68Se68/<wbr>OUTPUT',<br>
> > ><br>
> > > prefix='PbSe-360',<br>
> > ><br>
> > > pseudo_dir='/staging/op/NAREN_<wbr>USC/PbSe_360_FINAL_based_<br>
> ><br>
> > Pb68Se68/pseudo',<br>
> ><br>
> > > verbosity='low',<br>
> > ><br>
> > > /<br>
> > ><br>
> > ><br>
> > ><br>
> > > &SYSTEM<br>
> > ><br>
> > > ibrav=0,<br>
> > ><br>
> > > celldm(1)=90.7068539791d0,<br>
> > ><br>
> > > nat=360,<br>
> > ><br>
> > > ntyp=2,<br>
> > ><br>
> > > ecutwfc=30.0d0,<br>
> > ><br>
> > > ecutrho=120.0d0,<br>
> > ><br>
> > > input_dft='PBE',<br>
> > ><br>
> > > occupations='smearing',<br>
> > ><br>
> > > smearing='gaussian',<br>
> > ><br>
> > > degauss=0.002000d0,<br>
> > ><br>
> > > /<br>
> > ><br>
> > > &ELECTRONS<br>
> > ><br>
> > > diagonalization='david',<br>
> > ><br>
> > > mixing_mode='plain',<br>
> > ><br>
> > > mixing_beta=0.700d0,<br>
> > ><br>
> > > /<br>
> > ><br>
> > > &IONS<br>
> > ><br>
> > > /<br>
> > ><br>
> > > ATOMIC_SPECIES<br>
> > ><br>
> > > Pb 207.200000d0 Pb.pbe-hgh.UPF<br>
> > ><br>
> > > Se 78.960000d0 Se.pbe-hgh.UPF<br>
> > ><br>
> > > ATOMIC_POSITIONS {alat}<br>
> > ><br>
> > > Pb 0.4831100000d0 0.4740500000d0 0.4999300000d0<br>
> > ><br>
> > > Se 0.5190800000d0 0.5278700000d0 0.5981100000d0<br>
> > ><br>
> > > Se 0.5901900000d0 0.4712600000d0 0.2154800000d0<br>
> > ><br>
</div></div>> > > …………â<wbr>€¦â€¦â€¦â€¦ââ‚<wbr>¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬<wbr>¦â€¦â€¦â€¦â€¦<wbr>………<br>
> ><br>
> > ………….<br>
<div><div class="gmail-h5">> ><br>
> > > K_POINTS {gamma}<br>
> > ><br>
> > ><br>
> > ><br>
> > > CELL_PARAMETERS {alat}<br>
> > ><br>
> > > 1.000000000000d0 0.000000000000d0 0.000000000000d0<br>
> > ><br>
> > > 0.000000000000d0 1.000000000000d0 0.000000000000d0<br>
> > ><br>
> > > 0.000000000000d0 0.000000000000d0 1.000000000000d0<br>
> > ><br>
> > > *Output*<br>
> > ><br>
> > > iteration # 81 ecut= 30.00 Ry beta=0.70<br>
> > ><br>
> > > Davidson diagonalization with overlap<br>
> > ><br>
> > > WARNING: 9 eigenvalues not converged in regterg<br>
> > ><br>
> > > ethr = 4.62E-04, avg # of iterations = 21.0<br>
> > ><br>
> > ><br>
> > ><br>
> > > total cpu time spent up to now is 92680.3 secs<br>
> > ><br>
> > ><br>
> > ><br>
> > > total energy = 2098.58547221 Ry<br>
> > ><br>
> > > Harris-Foulkes estimate = -16225.87153481 Ry<br>
> > ><br>
> > > estimated scf accuracy < 209398.02191142 Ry<br>
> > ><br>
> > ><br>
> > ><br>
> > > iteration # 82 ecut= 30.00 Ry beta=0.70<br>
> > ><br>
> > > Davidson diagonalization with overlap<br>
> > ><br>
> > > WARNING: 5 eigenvalues not converged in regterg<br>
> > ><br>
> > > c_bands: 5 eigenvalues not converged<br>
> > ><br>
> > > ethr = 4.62E-04, avg # of iterations = 20.0<br>
> > ><br>
> > ><br>
> > ><br>
> > > total cpu time spent up to now is 95793.4 secs<br>
> > ><br>
> > ><br>
> > ><br>
> > > total energy = 1914.32044477 Ry<br>
> > ><br>
> > > Harris-Foulkes estimate = -18801.41916562 Ry<br>
> > ><br>
> > > estimated scf accuracy < 243341.55571758 Ry<br>
> > ><br>
> > ><br>
> > ><br>
> > > iteration # 83 ecut= 30.00 Ry beta=0.70<br>
> > ><br>
> > > Davidson diagonalization with overlap<br>
> > ><br>
> > > WARNING: 138 eigenvalues not converged in regterg<br>
> > ><br>
> > > ethr = 4.62E-04, avg # of iterations = 27.0<br>
> > ><br>
> > ><br>
> > ><br>
> > > total cpu time spent up to now is 99442.6 secs<br>
> > ><br>
> > ><br>
> > ><br>
> > > total energy = 1659.36438352 Ry<br>
> > ><br>
> > > Harris-Foulkes estimate = -15989.48139862 Ry<br>
> > ><br>
> > > estimated scf accuracy < 138246.99363207 Ry<br>
> > ><br>
> > > Any comment to help me getting started is very much appreciated!<br>
> > ><br>
> > ><br>
> > ><br>
> > > Best regards,<br>
> > ><br>
> > > Naren<br>
> > ><br>
> > ><br>
> > ><br>
> > ><br>
> > ><br>
> > ><br>
> > ><br>
> > > *Dr. Narendra Nath Ghosh*<br>
> > ><br>
> > > *Research Associate*<br>
> > ><br>
> > > *University of Gour Banga*<br>
> > ><br>
> > > *Department of Chemistry*<br>
> > ><br>
> > > *Malda-732102*<br>
> > ><br>
> > > *India*<br>
> > ><br>
> > > *Phone: +919126667601*<br>
> ><br>
> > ******************************<wbr>**************************<br>
> > - Article premier - Les hommes naissent et demeurent<br>
</div></div>> > libres et égaux en droits. Les distinctions sociales<br>
> > ne peuvent être fondées que sur l'utilité commune<br>
<span class="gmail-">> > - Article 2 - Le but de toute association politique<br>
> > est la conservation des droits naturels et<br>
</span>> > imprescriptibles de l'homme. Ces droits sont la liberté,<br>
> > la propriété, la sûreté et la résistance à l'oppression.<br>
<div class="gmail-HOEnZb"><div class="gmail-h5">> > ******************************<wbr>**************************<br>
> ><br>
> > Giuseppe Mattioli<br>
> > CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
> > v. Salaria Km 29,300 - C.P. 10<br>
> > I 00015 - Monterotondo Stazione (RM), Italy<br>
> > Tel + 39 06 90672342 - Fax +39 06 90672316<br>
> > E-mail: <<a href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>><br>
> > <a href="http://www.ism.cnr.it/en/staff/giuseppe-mattioli/" rel="noreferrer" target="_blank">http://www.ism.cnr.it/en/<wbr>staff/giuseppe-mattioli/</a><br>
> > ResearcherID: F-6308-2012<br>
> ><br>
> > ______________________________<wbr>_________________<br>
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<br>
******************************<wbr>**************************<br>
- Article premier - Les hommes naissent et demeurent<br>
libres et égaux en droits. Les distinctions sociales<br>
ne peuvent être fondées que sur l'utilité commune<br>
- Article 2 - Le but de toute association politique<br>
est la conservation des droits naturels et<br>
imprescriptibles de l'homme. Ces droits sont la liberté,<br>
la propriété, la sûreté et la résistance à l'oppression.<br>
******************************<wbr>**************************<br>
<br>
Giuseppe Mattioli<br>
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
v. Salaria Km 29,300 - C.P. 10<br>
I 00015 - Monterotondo Stazione (RM), Italy<br>
Tel + 39 06 90672342 - Fax +39 06 90672316<br>
E-mail: <<a href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>><br>
<a href="http://www.ism.cnr.it/en/staff/giuseppe-mattioli/" rel="noreferrer" target="_blank">http://www.ism.cnr.it/en/<wbr>staff/giuseppe-mattioli/</a><br>
ResearcherID: F-6308-2012<br>
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