<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
</head>
<body>
<style type="text/css" style="display:none;"><!-- P {margin-top:0;margin-bottom:0;} --></style>
<div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;font-family:Calibri,Helvetica,sans-serif;" dir="ltr">
<p>Dear Vivek,</p>
<p><br>
</p>
<p><span>In order to obtain accurate absorption spectra for solids, the Bethe-Salpeter approach is the right way to go. Nonetheless, please see my comments below.</span><br>
</p>
<p><br>
</p>
<p>epsilon.x is based on DFT and it is the code to compute absorption spectra in the independent-particle approximation, while turbo_lanczos.x and turbo_davidson.x are based on time-dependent DFT (TDDFT) and include interaction effects into account (it is possible
to disable interactions and obtain the same results as epsilon.x). Moreover, in epsilon.x the intensities are not fully correct, because there is a missing term in the commutator [V,r] (a contribution from the nonlocal part of the pseudo-potential is missing,
while in TDDFT codes above it is included). </p>
<p><br>
</p>
<p>Technical comments: you use a hybrid functional (<span>input_dft = 'pbe0'</span>), therefore you should use
<span>d0psi_rs = .true.</span> in <span>turbo_lanczos.x and turbo_davidson.x</span> in order to have the correct intensities in the absorption spectrum (this is true for molecules, while in solids it does not help).<br>
</p>
<p><br>
</p>
<p></p>
<div>> ATOMIC_SPECIES<br>
> Ti 47.867 Ti.upf<br>
> O 16.00 O.upf</div>
<p></p>
<p><br>
</p>
<p>Check this page for pseudos:</p>
<p><a href="https://www.materialscloud.org/discover/sssp/table/efficiency" class="OWAAutoLink" id="LPlnk452766" previewremoved="true">https://www.materialscloud.org/discover/sssp/table/efficiency</a></p>
<p><br>
</p>
<p>Greetings,</p>
<p>Iurii<br>
</p>
<p><br>
</p>
<div id="Signature">
<div id="divtagdefaultwrapper" dir="ltr" style="font-size: 12pt; color: rgb(0, 0, 0); font-family: Calibri, Helvetica, sans-serif, "EmojiFont", "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols;">
<div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0">
<div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0">
<font size="3" face="'Times New Roman', Times, serif" color="808080">--<br>
Dr. Iurii Timrov<br>
Postdoctoral Researcher<br>
<font color="808080"><font face="'Times New Roman', Times, serif"></font></font></font></div>
<font color="808080"></font>
<div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0">
<font size="3" face="'Times New Roman', Times, serif" color="808080">STI - IMX <font color="808080">
<font face="'Times New Roman', Times, serif">- THEOS</font></font></font><font size="3" face="'Times New Roman', Times, serif" color="808080"> and NCCR - MARVEL<br>
</font></div>
<div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0">
<font size="3" face="'Times New Roman', Times, serif" color="808080"><font size="3" face="'Times New Roman', Times, serif" color="808080">Swiss Federal Institute of Technology Lausanne (EPFL<font color="808080"><font face="'Times New Roman', Times, serif">)</font></font></font><br>
</font></div>
<font color="808080"></font>
<div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0">
<font size="3" face="'Times New Roman', Times, serif" color="808080">CH-1015 Lausanne, Switzerland<br>
+41 21 69 34 881</font></div>
<div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0">
<a href="http://people.epfl.ch/265334" tabindex="0" id="LPNoLP">http://people.epfl.ch/265334</a><br>
</div>
</div>
</div>
</div>
</div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Vivek Christhunathan <vivekppn@gmail.com><br>
<b>Sent:</b> Friday, February 14, 2020 12:24:25 PM<br>
<b>To:</b> users@lists.quantum-espresso.org<br>
<b>Subject:</b> [QE-users] Reg- Absorption spectrum using TDDFPT (turbo_davidson.x, turbo_lanczos.x and epsilon.x)</font>
<div> </div>
</div>
<div>
<div dir="ltr">
<div class="gmail_default"><span style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif">D</span><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif">ear QE users,</span><br>
</div>
<div class="gmail_default"><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif"><br>
</span></div>
<div class="gmail_default"><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif">Greetings!!!</span></div>
<div class="gmail_default"><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif"><br>
</span></div>
<div class="gmail_default"><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif">I am trying to find the absorption spectrum for the material 'TiO2' supercell (2*1*1) which consists of 24 atoms. I tried
a lot to find the absorption spectrum by reading all the related threads from QE. I have tried with all the methods such as turbo_davidson.x, turbo_lanczos.x and epsilon.x. I can only succeed with the use of epsilon.x but I am unable to get the same results
for the turbo_davidson.x and turbo_lanczos.x. I would like to know the reason behind this. And secondly to find an absorption spectrum of the material does epsilon.x method gives accurate results when compared with the other two? </span></div>
<div class="gmail_default"><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif"><br>
</span></div>
<div class="gmail_default"><span class="gmail_default" style="background-color:transparent;color:rgb(0,0,0);font-family:verdana,sans-serif">Thirdly I have tried it for the Zn doped TiO2 supercell. This time all the methods did not give a hand for my calculation. </span><font face="verdana, sans-serif">The
input files are given below. I would be very grateful if you help me out in this regard.</font><br>
</div>
<div class="gmail_default"><font face="verdana, sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="verdana, sans-serif">Please let me know if you need any further information. Looking forward to hearing from you.</font></div>
<div class="gmail_default"><font face="verdana, sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="verdana, sans-serif">Thanks in advance. </font></div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default"><span class="gmail-pl-c" style="box-sizing:border-box;color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">#</span><span style="color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">
self-consistent calculation</span> </div>
&control<br>
calculation = 'scf'<br>
prefix = 'TiO2'<br>
pseudo_dir = './'<br>
outdir = './outTiO2'<br>
!etot_conv_thr = 1e-5<br>
forc_conv_thr = 1e-4<br>
/<br>
&system<br>
ibrav = 0<br>
celldm(1) = 14.113<br>
nat = 24<br>
ntyp = 2<br>
ecutwfc = 80.0<br>
ecutrho = 800<br>
nbnd = 300<br>
input_dft = 'pbe0'<br>
/<br>
&electrons<br>
mixing_beta=0.3<br>
conv_thr = 1.0d-8<br>
diagonalization = 'david',<br>
mixing_mode = 'plain',<br>
/<br>
&IONS<br>
/<br>
&cell<br>
/<br>
CELL_PARAMETERS (alat)<br>
1.000927809 0.000000000 0.000000000<br>
0.000000000 0.500440909 0.000000000<br>
0.000000000 0.000000000 1.235414320<br>
ATOMIC_SPECIES<br>
Ti 47.867 Ti.upf<br>
O 16.00 O.upf<br>
ATOMIC_POSITIONS (<span class="gmail_default" style="font-family:verdana,sans-serif">crystal</span>)<br>
Ti 0.000000000 0.000000000 -0.000006420<br>
Ti 0.500000000 0.000000000 -0.000006418<br>
Ti 0.250000017 0.500000000 0.499993602<br>
Ti 0.750000015 0.500000000 0.499993602<br>
Ti 0.000000000 0.500000000 0.250006398<br>
Ti 0.500000000 0.500000000 0.250006394<br>
Ti 0.250000016 0.000000000 0.750006426<br>
Ti 0.750000016 0.000000000 0.750006426<br>
O 0.000000000 0.000000000 0.212511476<br>
O 0.500000000 0.000000000 0.212511476<br>
O 0.250000011 0.500000000 0.712511501<br>
O 0.750000021 0.500000000 0.712511501<br>
O 0.000000000 0.500000000 0.462514694<br>
O 0.500000000 0.500000000 0.462514705<br>
O 0.250000019 0.000000000 0.962514709<br>
O 0.750000013 0.000000000 0.962514709<br>
O 0.250000008 0.000000000 0.537488518<br>
O 0.750000024 0.000000000 0.537488518<br>
O 0.000000000 0.500000000 0.037488489<br>
O 0.500000000 0.500000000 0.037488487<br>
O 0.250000019 0.500000000 0.287485309<br>
O 0.750000013 0.500000000 0.287485309<br>
O 0.000000000 0.000000000 0.787485317<br>
O 0.500000000 0.000000000 0.787485307<br>
K_POINTS gamma<br>
<br>
<div class="gmail_default" style="font-family:verdana,sans-serif"><span class="gmail-pl-c" style="box-sizing:border-box;color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">#</span><span style="color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">
turbo_lanczos.x calculation</span><span style="font-family:Arial,Helvetica,sans-serif"> </span></div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><span style="font-family:Arial,Helvetica,sans-serif"> </span><span style="font-family:Arial,Helvetica,sans-serif">&lr_input</span></div>
prefix ='TiO2'<br>
outdir ='./outTiO2'<br>
!restart_step = 100,<br>
!restart = .true.<br>
/<br>
&lr_control<br>
itermax = 500<br>
ipol = 1<br>
!d0psi_rs = .true.<br>
/
<div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><span style="font-family:Arial,Helvetica,sans-serif"></span><span style="font-family:Arial,Helvetica,sans-serif"></span><span class="gmail-pl-c" style="box-sizing:border-box;color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">#</span><span style="color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">
turbo_spectrum.x calculation</span><span style="font-family:Arial,Helvetica,sans-serif"> </span><span style="font-family:Arial,Helvetica,sans-serif"><br>
</span>&LR_INPUT<br>
prefix = 'TiO2'<br>
outdir = './outTiO2'<br>
itermax0 = 500<br>
itermax = 10000<br>
extrapolation = 'osc'<br>
epsil = 0.01<br>
units = 1<br>
start = 0.0<br>
end = 4.0<br>
increment = 0.01<br>
ipol = 1<br>
/<br>
</div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><span style="font-family:Arial,Helvetica,sans-serif"></span><span class="gmail-pl-c" style="box-sizing:border-box;color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">#</span><span style="color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">
turbo_davidson.x calculation</span><span style="font-family:Arial,Helvetica,sans-serif"> </span></div>
<div class="gmail_default" style="font-family:verdana,sans-serif">&lr_input<br>
prefix = 'TiO2'<br>
outdir = './outTiO2'<br>
/<br>
&lr_dav<br>
!if_dft_spectrum = .false.<br>
num_eign = 5<br>
num_init = 10<br>
num_basis_max = 90<br>
residue_conv_thr = 1.0E-4<br>
start = 0.0 <br>
finish = 3.50<br>
step = 0.001<br>
broadening = 0.004<br>
reference = 0.3<br>
/<br>
<span style="font-family:Arial,Helvetica,sans-serif"></span><span style="font-family:Arial,Helvetica,sans-serif"></span><span class="gmail-pl-c" style="box-sizing:border-box;color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">#</span><span style="color:rgb(106,115,125);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">
turbo_spectrum.x calculation</span> </div>
<span class="gmail_default" style="font-family:verdana,sans-serif"></span>&lr_input<br>
prefix = 'TiO2'<br>
outdir = './outTiO2'<br>
td = 'davidson'<br>
epsil = 0.004<br>
start = 0.0d0 <br>
end = 3.5d0<br>
increment = 0.001d0<br>
eign_file = 'TiO2.eigen'<br>
<div class="gmail_default" style="font-family:verdana,sans-serif"><span style="font-family:Arial,Helvetica,sans-serif">/</span></div>
<div class="gmail_default" style="font-family:verdana,sans-serif"> <br>
</div>
<div>
<div dir="ltr" data-smartmail="gmail_signature">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div style="background-color:transparent;margin-top:0px;margin-bottom:0px"><font face="verdana, sans-serif"><span style="background-color:transparent;color:rgb(0,0,0)"><span class="gmail_default" style="font-family:verdana,sans-serif"></span>Kind Regards,</span><br>
</font></div>
<div style="background-color:transparent;margin-top:0px;margin-bottom:0px">
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">Vivek C</font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif"><br>
</font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">__________________________________</font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">Vivek Christhunathan</font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><span lang="EN-US"><font face="verdana, sans-serif">PhD researcher</font></span></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><span lang="EN-US"><font face="verdana, sans-serif">Mechanical Engineering</font></span></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><span lang="EN-US"><font face="verdana, sans-serif">College of Engineering and Informatics</font></span></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><span lang="EN-US"><font face="verdana, sans-serif">Room 2053</font></span></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif"><span lang="EN-US">Alice Perry Engineering Building</span><span lang="EN-US" style="color:rgb(51,102,255)"></span></font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif"><span lang="EN-US">National University of Ireland Galway</span><span lang="EN-US" style="color:rgb(51,102,255)"></span></font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><span lang="EN-US"><font face="verdana, sans-serif">Ireland</font></span></p>
</div>
<div dir="ltr" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">E-mail: <a href="mailto:v.christhunathan1@nuigalway.ie" target="_blank">
v.christhunathan1@nuigalway.ie</a></font></div>
<div dir="ltr" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">Phone: +353 899811181, +91 9600752742</font></div>
<div dir="ltr" style="color:rgb(0,0,0);font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif,EmojiFont,"Apple Color Emoji","Segoe UI Emoji",NotoColorEmoji,"Segoe UI Symbol","Android Emoji",EmojiSymbols">
<img src="https://docs.google.com/uc?export=download&id=1oPtxd7PT5ljQRnuP-Gdf5upjiKPXk7Fz&revid=0B_S3ZLbRRu26NW1YallITFk1ZHMxaStQaUVoMjZ4M2NqcC9BPQ"><br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</body>
</html>