<div dir="ltr"><div><div><div><div><div>ohhh, sorry Prof. Peter.<br><br></div>(sp) was included by mistake. I forgot to delete it.<br><br></div>For Pb(5p): When I initialized the case I for one 5P state as core(T) and other as valance (F).<br></div>The total charge leakage (not in the initialization bu it was observed in the *.outputst file) was 0.00068 with -6.0 ecut and with -7.5 it was 0.000126. So I thought it would be better it I use -7.5 ecut.<br><br></div>However, I will now use -ecut as -6.0.<br><br></div>I think now the step I am going to follow are fine??<br><br><br><div class="gmail_extra">One query was unanswered:<br><br>
how iqtlsave will change the calculation if I choose it as "0"?<br clear="all"></div><div class="gmail_extra"><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><span style="color:rgb(0,0,0)"><br>Bhamu</span></div></div></div></div></div></div></div></div></div></div></div>
<br><div class="gmail_quote">On Thu, Nov 10, 2016 at 10:35 PM, Peter Blaha <span dir="ltr"><<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien.ac.at</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">Why would you do a runsp_lapw for a non-magnetic system ???<br>
<br>
Spin-orbit is also active for a non-magnetic material.<br>
<br>
Don't mix up spin-polarization with spin-orbit ....<br>
<br>
PS: I'm also not sure why you want to include the Pb-5p state as valence ?? I don't think you have to use so small Pb spheres that you get core leakage ?? And with Pb-5p as core you have the full SO-splitting inluded, ....<br>
<br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
D.<br>
<br>
1. initso_lapw<br>
2. runsp_lapw -so -p -i 40 -ec 0.0001 -cc 0.0001' Fine ????<br>
<br>
I am using both step C and D differently because Dr. Tran suggested for<br>
the same<br>
(<a href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg03843.html" rel="noreferrer" target="_blank">http://www.mail-archive.com/w<wbr>ien@zeus.theochem.tuwien.ac.at<wbr>/msg03843.html</a>)<br>
<br>
<br>
One more question:<br>
how iqtlsave will change the calculation if I coose it as "0"?<br>
<br>
Kind regards<br>
<br>
<br>
<br>
------------------------------<wbr>------------------<br>
Dr. K. C. Bhamu<br>
(UGC-Dr. D. S. Kothari Postdoc Fellow)<br>
Department of Physics<br>
Goa University, Goa-403 206<br>
India<br>
Mob. No. +91-9975238952<br>
<br>
On Thu, Nov 10, 2016 at 8:00 PM, Peter Blaha<br>
<<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien.ac.at</a> <mailto:<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien<wbr>.ac.at</a>>> wrote:<br>
<br>
Very good explanation.<br>
<br>
So you should probably use SO + mBJ and see what comes out then ....<br>
(you should get again a good band gap, although effective masses are<br>
not necessarily improved by mBJ ...)<br>
<br>
Am 10.11.2016 um 15:24 schrieb John McLeod:<br>
<br>
I have some experience using WIEN2k for metal organic halide<br>
perovskites.<br>
<br>
PBE without SOC gets the correct band gap for CH3NH3PbI3 (which<br>
I assume<br>
is the compound Dr. Bhamu is studying) because of a "fortuitous"<br>
error<br>
cancellation between using PBE and ignoring SOC. This is<br>
reasonably well<br>
known and has been studied in detail in several manuscripts. SOC+PBE<br>
results in a significantly underestimated band gap, as one might<br>
expect.<br>
<br>
I assume Dr. Bhamu is using the calculated low frequency dielectric<br>
constant (e*), and the calculated effective mass (m*) to<br>
estimate the<br>
binding energy using the simple Mott-Wannier model: E_ex =<br>
m*/e^2 (13.6)<br>
eV .<br>
<br>
SOC does modify the shape of the bands near the gamma-point (I<br>
believe<br>
it reduces the effective mass), and SOC also influences the<br>
dielectric<br>
constant. So I think perhaps including SOC and using a scissors<br>
operation with OPTIC to get the correct band gap may be the most<br>
straight-forward (if not completely ab initio) method.<br>
<br>
Have you looked at F. Brivio, et al., Phys. Rev. B 89 155204 (DOI:<br>
10.1103/PhysRevB.89.155204)?<br>
They go into some detail about different approaches, it may be<br>
helpful<br>
for your present situation.<br>
<br>
Regards,<br>
-John McLeod<br>
<br>
So I do not think SOC can be<br>
On 2016-11-10 10:02 PM, Peter Blaha wrote:<br>
<br>
I'm not the expert on that topic, but I think you mix up the two<br>
dielectric constants, which could be a semantic problem. To<br>
compare<br>
with a classic experiment, you may need to obtain the ionic<br>
contribution to the dielectric constant, which as far as I<br>
know can be<br>
done using BERRYPI.<br>
<br>
Other comments:<br>
To obtain the "correct" band gap using PBE is very<br>
"unusual". For most<br>
materials (but of course there could be exemptions) the PBE<br>
band gaps<br>
should be ~50% smaller than experiment.<br>
<br>
Pb ??? this is very "relativistic" ! Did you consider spin-orbit<br>
coupling ?<br>
<br>
And last but not least, I have no idea how you calculate exciton<br>
binding energies from a single particle spectrum. We would<br>
do this<br>
using BSE calculations, but your system is probably too<br>
complicated<br>
for this.<br>
<br>
Am 10.11.2016 um 14:26 schrieb Dr. K. C. Bhamu:<br>
<br>
Dear Prof. Peter and Experts<br>
This is with some more information:<br>
<br>
To put a joint paper on complex Metal-organic halide<br>
perovskites, I am<br>
trying to reproduce some experimental results measured by my<br>
collaborator.<br>
<br>
For my complex system, I got low frequency dielectric<br>
constant value of<br>
~5.6 (at 0.013 eV) and the calculated the exciton<br>
binding energy ~0.087<br>
- 0.095 eV (85 -97 meV). This is too high because the<br>
measurements here<br>
get about 13 meV and a 1-2 transition of ~9.9 meV<br>
(measured).<br>
<br>
In literature the reported static and optical dielectric<br>
constants for<br>
the system are in the range of 17-24 and 4.5-6.5<br>
respectively using DFT.<br>
<br>
In my case the zero frequency dielectric constant (~<br>
5.6) is in tune<br>
with the optical dielectric constants (4.5-6.5).<br>
<br>
I think my value ~5.6 should be in the range of 17-24.<br>
*Is it so?*<br>
Please help me to understand it.<br>
<br>
I used PBE functional with 4x4x4 k mesh. I reduced rmt<br>
by 5% and then<br>
rmt for Pb and I were reduced by a factor of 0.3. I have<br>
doubt here??<br>
<br>
My band gap is in reasonable agreement with the<br>
experimentally observed<br>
band gap (1.57eV) +/- 0.1.<br>
<br>
The problem may be that my epsilon value (~5.6) is too<br>
low and I looked<br>
up our local measured value of ~18 for the low frequency<br>
part. If I use<br>
this value (18) then much better exciton binding<br>
energies come out.<br>
<br>
What can be an mistake that I may did in calculation? or<br>
may it be a<br>
reason of the device fabrication because for<br>
experimental part some<br>
p-i-n and n-i-p type device has been framed?<br>
<br>
<br>
Kind regards<br>
<br>
Bhamu<br>
<br>
<br>
<br>
<br>
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