Dear Shamik, I think it would be aNew * bNew * cNew = volumeNew a * b * c = volumeOriginal bNew/aNew = bA = b/a cNew/aNew = cA = c/a
volumeNew = aNew * (Aew * bA) * (aNew * cA) = = aNew^3 * bA*cA volume = a * (a * bA) * (a * cA) = a^3 * bA * cA volumeNew / volume = (aNew/a)^3 If this is your x-parameter, then I was originally thinking that you have forgotten to take into account the cAnew and bAConst dividing the original volume when optimizing c/a at constant b/a and volume in the next step. But now, looking at your structure file I suspect this: Your lattice parameters a and b from your structure file are very similar. The ratio bNew / aNew in your optimized structure file is 11.699299 bohr / 11.264662 bohr = 1.038584 This is rather close to the ratio of your volumes before and after c/a optimization at constant volume: 2146.485 bohr^3 / 2058.7690 bohr^3 = 1.042606 Perhaps, if you tried to optimize c/a at constant volume and constant b/a using x optimize you might do a misprint and choose option 2 in x optimize instead of option 3. Is this possible? But then, you should have a and b the same in your structure file (and you have not) However, the a and b could become again different after applying another b/a optimization at constant volume and c/a. Or, if you did it manually you could somehow interchange a and b lattice parameters when recalculating them. Is this possible? HTH Tomas ---------- Původní e-mail ---------- Od: shamik chakrabarti <[email protected]> Komu: A Mailing list for WIEN2k users <[email protected]> Datum: 12. 6. 2020 17:33:19 Předmět: Re: [Wien] Volume has changed during running optimization of c/a with constant volume & b/a Another thing is that from volume optimization the unit cell volume is coming as 1073.2425 bohr^3 which get doubles when we consider the volume of a conventional cell to become 2146.485 bohr^3 while the printed volume of a conventional unit cell after c/a optimization is coming as 2058.7690 bohr^3 ; Why is this discrepancy? Is it that the conventional cell volume about 1.9183 times the unit cell volume & not as I have assumed. I am sending the fully optimized struct (according to my calculation) file for your consideration. with regards, On Fri, 12 Jun 2020 at 20:46, shamik chakrabarti <[email protected]> wrote: Dear Tomas, Can you please elaborate how to know a', b' and c' (the final lattice parameters) from a unit cell volume optimization with a:b:c = constant (where a, b, c are initial lattice parameters) ? with regards, On Fri, 12 Jun 2020 at 17:15, Tomas Kana <[email protected]> wrote: Dear Shamik, Ok, I undestand your point. But anyway, I think, that the problem comes from your equation. If you want to relax c/a with constant volume and constant b/a then I would prefer these eqations: original c/a = cAoriginal b/a = bAconstant new c/a = cAnew original volume a*b*c new volume (the same as original) aNew * bNew * cNew = aNew * (aNew * bAConstant) * (aNew * cAnew) = aNew^3 * bAConsant*cAnew = original volume You choose your desired cAnew and know0 bAconstant and the original volume. In this way, you obtain the aNew and it is easy to obtain bNew and cNew then. But I still do not understand the parameter x in your eqation. Maybe this could be the source of your error? Hope this helps Tomas Dear Tomas, I am sorry to say that you have misunderstood my equation. I have used abcx^3 = a'b'c' where a', b' and c' are the new lattice parameters & not the old a,b,c !!! :) with regards, On Fri, 12 Jun 2020 at 16:31, Tomas Kana <[email protected]> wrote: Dear Shamik, If you want to keep a constant volume and you use the equation abcx^3 = 332.934 = abc then only one solution is possible: x = 1. ax = a, bx = b cx = c. Your equation does not make sense to me.... With best regards Tomas Kana where a, b, c are the initial lattice parameters. From that equation I have found the value of x & then finally multiply x with each lattice parameters to get new lattice parameters as a* = ax, b*=bx & c*=cx & then put ---------- Původní e-mail ---------- Od: shamik chakrabarti <[email protected]> Komu: A Mailing list for WIEN2k users <[email protected]> Datum: 12. 6. 2020 10:05:37 Předmět: Re: [Wien] Volume has changed during running optimization of c/a with constant volume & b/a No, I have created a new directory for c/a optimization. I have done the followings, abcx^3 = 332.934 where a, b, c are the initial lattice parameters. From that equation I have found the value of x & then finally multiply x with each lattice parameters to get new lattice parameters as a* = ax, b*=bx & c*=cx & then put a*, b* & c* as new inputs for c/a optimization with constant volume in a new directory. with regards, On Fri, 12 Jun 2020 at 13:23, Peter Blaha <[email protected]> wrote: How did you do: "putting the lattice parameters as input for c/a optimization" ??? If you continue in the previous directory, do you realize that there is a case_initial.struct which, if present, is taken a "base struct file". Am 12.06.2020 um 04:12 schrieb shamik chakrabarti: > Dear wien2k users, > > I am running wien2k 19.1. I have started c/a optimization > with constant volume and b/a for an ABO4 compound. From volume > optimization with a:b:c=constant I have obtained an unit cell volume of > 332.934 Ang^3. While after calculation of lattice parameters and putting > the lattice parameters as input for c/a optimization with *constant > volume* & b/a, the printed unit cell volume is coming as 312.8004 Ang^3. > > Where I am doing wrong? > > Thanks in advance. > > with regards, > -- > Dr. Shamik Chakrabarti > Research Fellow > Department of Physics > Indian Institute of Technology Patna > Bihta-801103 > Patna > Bihar, India > > _______________________________________________ > Wien mailing list > [email protected] > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/[email protected]/index.html > -- Peter Blaha Inst.Materials Chemistry TU Vienna Getreidemarkt 9 A-1060 Vienna Austria +43-1-5880115671 _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html _______________________________________________ Wien mailing list [email protected] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/[email protected]/index.html
