<div dir="ltr">Dear Prof. Blaha,<div><br></div><div> Thank you so much for your elaborate reply. This will be very helpful for me.</div><div><br></div><div>Thanks once again.</div><div><br></div><div>with regards,</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, 10 Mar 2020 at 17:23, Peter Blaha <<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">I think F. Tran already gave you the hint about "primitive R cell" and <br>
"conventional H cell".<br>
<br>
The volume of the R cell is 3 times smaller than that of the H cell.<br>
<br>
Wien2k gives H lattice parameters, but makes the calculation internally <br>
in R cell.<br>
<br>
So yes, if you get an equilibrium volume which does not fit your <br>
expectations, it is because of your wrong assumptions aber the actual <br>
lattice.<br>
<br>
It is the same as for a FCC cubic cell: What is the volume of the <br>
primitive (R) cell of an FCC lattice: it is NOT a**3, but a**3 / 4.<br>
<br>
--------------------<br>
Besides this: the optimize scribt gives you a volume, but of course also <br>
total energies and you can easily see, which of your struct files <br>
corresponds (nearly) to the optimized volume (the one with the lowest <br>
energy). And you find the corresponding a,c values directly in this <br>
struct file.....<br>
<br>
It can't be that difficult to get the optimized lattice parameters.<br>
<br>
PS: Please read the UG (struct file) about R-lattices<br>
<br>
On 3/10/20 11:03 AM, shamik chakrabarti wrote:<br>
> I think we should multiply the printed volume by 3 to get the actual <br>
> volume as the cell described in rhombohedral lattice is 3 times larger <br>
> than the hexagonal unit cell...I am sending a link which gives this clue<br>
> <br>
> <a href="http://www.globalsino.com/EM/page3546.html" rel="noreferrer" target="_blank">http://www.globalsino.com/EM/page3546.html</a><br>
> <br>
> Please correct me if I am wrong!<br>
> <br>
> with regards,<br>
> <br>
> On Tue, 10 Mar 2020 at 15:22, Tran, Fabien <<a href="mailto:fabien.tran@tuwien.ac.at" target="_blank">fabien.tran@tuwien.ac.at</a> <br>
> <mailto:<a href="mailto:fabien.tran@tuwien.ac.at" target="_blank">fabien.tran@tuwien.ac.at</a>>> wrote:<br>
> <br>
> Probably. In case.struct, the lattice constants and angles are for<br>
> the hexagonal cell, while atoms positions are with respect to<br>
> rhombohedral.<br>
> <br>
> <br>
> ------------------------------------------------------------------------<br>
> *From:* Wien <<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.theochem.tuwien.ac.at</a><br>
> <mailto:<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.theochem.tuwien.ac.at</a>>> on behalf of<br>
> shamik chakrabarti <<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a><br>
> <mailto:<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a>>><br>
> *Sent:* Tuesday, March 10, 2020 10:46 AM<br>
> *To:* A Mailing list for WIEN2k users<br>
> *Subject:* Re: [Wien] Volume optimization of Sulphur<br>
> It may be a clue for solving the above problem;<br>
> <br>
> In the struct file (as seen in the GUI) a line<br>
> remains added : "positions must be specified in rhombohedral<br>
> coordinates!"<br>
> <br>
> Looking forward to your response eagerly.<br>
> <br>
> with regards,<br>
> <br>
> On Tue, 10 Mar 2020 at 14:51, shamik chakrabarti<br>
> <<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a> <mailto:<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a>>> wrote:<br>
> <br>
> Dear Prof. Tran,<br>
> <br>
> a^2 c Sin 60 is the volume of the<br>
> rhombohedral cell having lattice parameter a=b & c. I have used<br>
> the same formula for hexagonal SnS2 and got very good results. I<br>
> think somehow the printed volume is almost 1/2.8 th of the<br>
> actual value needed. I guess it is something related to R_3<br>
> crystal system...........<br>
> <br>
> with regards,<br>
> <br>
> On Tue, 10 Mar 2020 at 14:36, Tran, Fabien<br>
> <<a href="mailto:fabien.tran@tuwien.ac.at" target="_blank">fabien.tran@tuwien.ac.at</a> <mailto:<a href="mailto:fabien.tran@tuwien.ac.at" target="_blank">fabien.tran@tuwien.ac.at</a>>> wrote:<br>
> <br>
> WIEN2k does the calculations in the primitive unit cell,<br>
> whose volume is given by :VOL in case.scf<br>
> <br>
> Is a^2 c Sin 60 not the volume of the conventional cell?<br>
> <br>
> You can visualize the primitive and conventional cells of<br>
> case.struct with xcrysden (press F3 or F4).<br>
> <br>
> <br>
> ------------------------------------------------------------------------<br>
> *From:* Wien <<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.theochem.tuwien.ac.at</a><br>
> <mailto:<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.theochem.tuwien.ac.at</a>>> on behalf<br>
> of shamik chakrabarti <<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a><br>
> <mailto:<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a>>><br>
> *Sent:* Tuesday, March 10, 2020 9:58 AM<br>
> *To:* A Mailing list for WIEN2k users<br>
> *Subject:* Re: [Wien] Volume optimization of Sulphur<br>
> Dear Wien2k users,<br>
> <br>
> I am also certain that I am<br>
> not doing any mistake in the formula of Volume=a^2 c Sin<br>
> 60. However, the V0 printed in the window showing the fitted<br>
> BM curve is coming much less than that expected from a^2 c<br>
> Sin 60 . What could be the cause? Is it related to the space<br>
> group R_3 (space group no. 148)?<br>
> <br>
> Looking forward to your reply eagerly.<br>
> <br>
> with regards,<br>
> <br>
> <br>
> On Tue, 10 Mar 2020 at 13:11, shamik chakrabarti<br>
> <<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a> <mailto:<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a>>><br>
> wrote:<br>
> <br>
> Dear Lyudmila Sir,<br>
> <br>
> To remove the confusion I am<br>
> sending the struct file which have been used in our<br>
> simulation. I have good results as far as the volume<br>
> optimization curve is concerned. However, while<br>
> calculating the lattice parameters using the formula V =<br>
> a^2 c sin60 I got the low value of lattice parameters.<br>
> My query is<br>
> (1) Whether I have done something wrong in the formula<br>
> itself?<br>
> (2) While GGA is better than nlvdw in this case?<br>
> <br>
> with regards,<br>
> <br>
> -- <br>
> Dr. Shamik Chakrabarti<br>
> Research Fellow<br>
> Department of Physics<br>
> Indian Institute of Technology Patna<br>
> Bihta-801103<br>
> Patna<br>
> Bihar, India<br>
> <br>
> <br>
> <br>
> -- <br>
> Dr. Shamik Chakrabarti<br>
> Research Fellow<br>
> Department of Physics<br>
> Indian Institute of Technology Patna<br>
> Bihta-801103<br>
> Patna<br>
> Bihar, India<br>
> _______________________________________________<br>
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> <br>
> <br>
> <br>
> -- <br>
> Dr. Shamik Chakrabarti<br>
> Research Fellow<br>
> Department of Physics<br>
> Indian Institute of Technology Patna<br>
> Bihta-801103<br>
> Patna<br>
> Bihar, India<br>
> <br>
> <br>
> <br>
> -- <br>
> Dr. Shamik Chakrabarti<br>
> Research Fellow<br>
> Department of Physics<br>
> Indian Institute of Technology Patna<br>
> Bihta-801103<br>
> Patna<br>
> Bihar, India<br>
> _______________________________________________<br>
> Wien mailing list<br>
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> <br>
> <br>
> <br>
> -- <br>
> Dr. Shamik Chakrabarti<br>
> Research Fellow<br>
> Department of Physics<br>
> Indian Institute of Technology Patna<br>
> Bihta-801103<br>
> Patna<br>
> Bihar, India<br>
> <br>
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> <br>
<br>
-- <br>
<br>
P.Blaha<br>
--------------------------------------------------------------------------<br>
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna<br>
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982<br>
Email: <a href="mailto:blaha@theochem.tuwien.ac.at" target="_blank">blaha@theochem.tuwien.ac.at</a> WIEN2k: <a href="http://www.wien2k.at" rel="noreferrer" target="_blank">http://www.wien2k.at</a><br>
WWW: <a href="http://www.imc.tuwien.ac.at/TC_Blaha" rel="noreferrer" target="_blank">http://www.imc.tuwien.ac.at/TC_Blaha</a><br>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:small">Dr. Shamik Chakrabarti</div><div style="font-size:small">Research Fellow </div><div style="font-size:small">Department of Physics</div><div style="font-size:small">Indian Institute of Technology Patna</div><div style="font-size:small">Bihta-801103</div><div style="font-size:small">Patna</div><div style="font-size:small">Bihar, India</div></div></div></div></div></div></div></div>