<div dir="ltr"><div><div><div>Dear Prof. Gerhard and Stefaan,<br><br></div>As the system is complex so to save my wall time, I need a confirmation what I am following.<br></div><div><br></div><div>In a fresh calculation, after a structure relaxation, I have done C/A optimization [VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice)].</div><div><br></div><div>The new optimization values are given below. It gives <br></div><div><br></div><div>Minimum value of C/A is = 0.983596</div><div><br></div><div>so this means that (C/A)_new =983596 (say "X")<br></div><div><br></div><div><br></div><div>C_new=(X)*(A_new). #A_new is taken from below set of data.</div><div><br></div><div><br></div><div>Should I go this way or A should be the old one?</div><div><br></div><div><br></div><div><br></div><div><br></div><div>Now update this C_new in struct file and then go for B/A optimization. followed by volume optimization to get optimised A.</div><div><br></div><div><br></div><div><br></div><div><br></div><br>Minimum value of C/A is = 0.983596 >>> minmum value of C/A<br>Minimum value of ENE is = -339059.101281 Ry</div><div>==========================================================<br>Value of A is = 14.66061 bohr ; 7.75806 Ang >> A_new<br>Value of B is = 21.69275 bohr ; 11.47931 Ang <br>Value of C is = 14.42012 bohr ; 7.63080 Ang<br> ==========================================================<br>Initial value of C/A is = 0.973598<br>Conv. Unit Cell Vol = 4586.0140 bohr^3 ; 679.5773 Ang^3<br> ==========================================================<br><br></div><br><div><br><br></div><div class="gmail_extra">Regards</div><div class="gmail_extra"><br></div><div class="gmail_extra">Bhamu</div><div class="gmail_extra"><br></div><div class="gmail_extra"><br></div><div class="gmail_extra"><div class="gmail_quote">On Fri, Oct 13, 2017 at 5:40 PM, Stefaan Cottenier <span dir="ltr"><<a href="mailto:Stefaan.Cottenier@ugent.be" target="_blank">Stefaan.Cottenier@ugent.be</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><span lang="EN-US">No, not really. You have three (unit cell) degrees of freedom: E(a,b,c). Or similarly E(V, b/a, c/a) (with V=a*b*c). The different options in optimize_lapw give you a series of unit
cells with either different values of V (and b/a and c/a constant), different values of b/a (and V and c/a constant) and different values of c/a (and V and b/a constant). These are three slices through the energy landscape. By finding the energy minimum along
one slice, fix it, then go on with the next slice, etc. … you can gradually approach the absolute energy minimum. It might take several iterations through this scheme if your starting cell is far away from the minimum. Best is to start first with the degree
of freedom that affects energy most (usually the volume). <u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Stefaan<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><a name="m_-1354330653578882112__MailEndCompose"><span lang="EN-US"><u></u> <u></u></span></a></p>
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<p class="MsoNormal"><b><span lang="NL">Van:</span></b><span lang="NL"> Wien [mailto:<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.<wbr>theochem.tuwien.ac.at</a>]
<b>Namens </b>Dr. K. C. Bhamu<br>
<b>Verzonden:</b> vrijdag 13 oktober 2017 14:04<br>
<b>Aan:</b> A Mailing list for WIEN2k users <<a href="mailto:wien@zeus.theochem.tuwien.ac.at" target="_blank">wien@zeus.theochem.tuwien.ac.<wbr>at</a>><br>
<b>Onderwerp:</b> Re: [Wien] optimization of an orthorhombic cell<u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Thank you very much for a hint.<u></u><u></u></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">I thought the value obtained from "VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice)" are well optimised then why I do need to optimise all of them again.<br>
<br>
<u></u><u></u></p>
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<p class="MsoNormal">Now I see, B/A scaling will give us optimised b, then C/A scaling will give us optimised C and finally optimised v(=a*b*c) will give us optimised "a".<u></u><u></u></p>
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<p class="MsoNormal">Using optimised a,b,c structure relaxation will be done.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">I should be fine to optimised an orthorhombic cell. Is it?<u></u><u></u></p>
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<p class="MsoNormal"><br>
<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Regards<u></u><u></u></p>
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<p class="MsoNormal">Bhamu<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">On Fri, Oct 13, 2017 at 11:18 AM, Fecher, Gerhard <<a href="mailto:fecher@uni-mainz.de" target="_blank">fecher@uni-mainz.de</a>> wrote:<u></u><u></u></p>
<blockquote style="border:none;border-left:solid #cccccc 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm">
<p class="MsoNormal">you have three quantities V=a*b*c, b=a*(b/a) and c=a*(c/a)<br>
so what is the problem ?<br>
<br>
Ciao<br>
Gerhard<br>
<br>
DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:<br>
"I think the problem, to be quite honest with you,<br>
is that you have never actually known what the question is."<br>
<br>
==============================<wbr>======<br>
Dr. Gerhard H. Fecher<br>
Institut of Inorganic and Analytical Chemistry<br>
Johannes Gutenberg - University<br>
55099 Mainz<br>
and<br>
Max Planck Institute for Chemical Physics of Solids<br>
01187 Dresden<br>
______________________________<wbr>__________<br>
Von: Wien [<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.theochem.<wbr>tuwien.ac.at</a>] im Auftrag von Dr. K. C. Bhamu [<a href="mailto:kcbhamu85@gmail.com" target="_blank">kcbhamu85@gmail.com</a>]<br>
Gesendet: Freitag, 13. Oktober 2017 00:42<br>
An: A Mailing list for WIEN2k users<br>
Betreff: Re: [Wien] optimization of an orthorhombic cell<br>
<br>
Dear List,<br>
<br>
<br>
Could you please help me to get optimize lattice parameters from the procedure that I followed as mentioned below:<br>
<br>
<br>
<br>
The procedure is a four-step task what I am following:<br>
<br>
The original lattice parameters were: a, b, c=16.763005, 24.803600, 16.320431 >> vol 6785.64777697697 bohr^3.<br>
<br>
<br>
1. VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice)<br>
<br>
getting below optimized data:<br>
=============================<wbr>=============================<br>
Lowest point on X-axis is = -1.615800<br>
Minimum value of B/A is = 1.455755<br>
Minimum value of ENE is = -339059.104498 Ry<br>
=============================<wbr>=============================<br>
Value of A is = 16.85428 bohr ; 8.91890 Ang<br>
Value of B is = 24.53569 bohr ; 12.98373 Ang<br>
Value of C is = 16.40929 bohr ; 8.68342 Ang<br>
=============================<wbr>=============================<br>
Initial value of B/A is = 1.479663<br>
Conv. Unit Cell Vol = 6785.7557 bohr^3 ; **********Ang^<br>
<br>
<br>
2. Volume optimization using option 1 in "x optimize" and then calculating new volume from eplot option.<br>
<br>
<br>
Query: Step two is giving optimized volume but I do not know how to calculate lattices parameters from a single volume<br>
value for the next step "VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice)"?<br>
<br>
<br>
The original cell volume and lattice parameters are mentioned at the beginning.<br>
<br>
and the new volume from step two is: 6815.3427 bohr^3<br>
<br>
<br>
<br>
The above same query is for the remaining process:<br>
<br>
3. optimization of C/A<br>
<br>
4. optimization of V.<br>
<br>
<br>
*5 At the final step I will do structural relaxation (min_.....).<br>
<br>
<br>
Could you please advice me how to proceed?<br>
<br>
<br>
<br>
Kind regards,<br>
Bhamu<br>
<br>
<br>
<br>
<br>
<br>
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