[Wien] Doubts regarding the volume optimization of a triclinic cell

[Laurence Marks]

Also, the relevance of the results goes as exp(-time*1,000,000) so after 11
years the Professor has probably moved to another country.

I am 100% certain that you are worrying about details which do not matter:
a) DFT lattice parameters are rarely better than 0.5%.
b) DFT energies are rarely better than 4kJ/atom mole in accuracy.
c) Electronic states are rarely better than 0.1 eV, as DFT is ground state.

Accept that you calculations are only good approximations.

"All things appear and disappear because of the concurrence of causes and
conditions. Nothing ever exists entirely alone: everything is in
relationship to everything else."

-- Gautama Buddha
In Dwight Goddard, Buddha, Truth and Brotherhood (1934)

---
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
"Research is to see what everybody else has seen, and to think what
nobody else has thought" Albert Szent-Györgyi

On Sat, Oct 23, 2021, 6:09 AM Gavin Abo <gabo13279 at gmail.com> wrote:

> I follow that your lattice parameters a=18.508 Bohr, b=39.835 Bohr,
> c=40.199 Bohr, α=119.701 degrees, β=103.309 degrees, and γ=90.0 degrees
> using the equation at [1] give you
>
> Volume_triclinic = 18.508 Bohr*39.835 Bohr*40.199 Bohr*sqrt(1-cos(119.701
> degrees *(π radians/180 degrees))^2-cos(103.309*(π radians/180
> degrees))^2-cos(90.0*(π radians/180 degrees))^2+2*cos(119.701 degrees *(π
> radians/180 degrees))*cos(103.309 degrees *(π radians/180
> degrees))*cos(90.0 degrees *(π radians/180 degrees))) ≈ 24823 Bohr^3.
>
> I also remember reading that the :VOL in case.scf is for the primitive
> unit cell [2-4].
>
> Regarding the 20805.429 Bohr^3, I don't seem to be seeing enough
> information regarding that.  Thus, I'm unable to follow where you are
> getting that from.
>
> I have seen the post at [5] describing how a triclinic optimization could
> be done.
>
> However, in addition to that post I have read other posts about how it
> requires too many calculations for triclinic such that it not likely
> reasonably possible to do [6-8].
>
> For example, say your advising professor says he needs a triclinic
> optimization one week from now.  However, say it takes 1 day to run and
> complete a single calculation on your initial triclinic structure.  Now, if
> you fixed b, c, α, β, γ and varied lattice constant a with four different
> values you would expect those calculations to take about 4 days.  However,
> to fully optimize the structure you would also need to vary b, c, α, β, and
> γ as well such that you would need to do 4096 calculations in total as
> explained in [5].
>
> Thus, you could estimate that it would take 4096 days or about 11 years
> (=4096/365.25).  So it not possible to meet the professors deadline, but
> the calculation is possible but would take 11 years.  However, another
> problem with that could be that you run out of hard drive space and cannot
> afford the cost to buy more hard drives to store the data from all those
> 4096 calculations.
>
> Furthermore, if you are like me, where I sometimes mess up my calculation
> setup during initialization (init_lapw).  I would probably check the result
> after 11 years to find out I setup the calculation wrong and have to start
> over.
>
> So for me it would probably end up similar to the scenerio in The
> Hitchhiker's Guide to the Galaxy where my GIGO [9] mistake during
> initialization would end with a result like 42 [10].
> [1] https://www.globalsino.com/EM/page3033.html
> <https://urldefense.com/v3/__https://www.globalsino.com/EM/page3033.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf0dtnXmlg$>
> [2]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg20184.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg20184.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf3ka8_EwA$>
> [3]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14487.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14487.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf3SHP8f1Q$>
> [4]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg19755.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg19755.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf2z1QAvAA$>
> [5]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10777.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10777.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf07_GLANw$>
> [6]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg01914.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg01914.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf2Xv6IO2w$>
> [7]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10505.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10505.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf1is5Zeqg$>
> [8]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg21450.html
> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg21450.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf1W4CqnGQ$>
> [9] https://en.wikipedia.org/wiki/Garbage_in,_garbage_out
> <https://urldefense.com/v3/__https://en.wikipedia.org/wiki/Garbage_in,_garbage_out__;!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf0XPlwD1w$>
> [10]
> https://en.wikipedia.org/wiki/Phrases_from_The_Hitchhiker%27s_Guide_to_the_Galaxy#The_Answer_to_the_Ultimate_Question_of_Life,_the_Universe,_and_Everything_is_42
> <https://urldefense.com/v3/__https://en.wikipedia.org/wiki/Phrases_from_The_Hitchhiker*27s_Guide_to_the_Galaxy*The_Answer_to_the_Ultimate_Question_of_Life,_the_Universe,_and_Everything_is_42__;JSM!!Dq0X2DkFhyF93HkjWTBQKhk!Em14IGppgbfioraJ-l3bMy9gwwMoftlHrzxjMWzvPLGE8PfWKZv3GTl3xlrwxf0fr_h39g$>
>
> On 10/23/2021 1:18 AM, Anupriya Nyayban wrote:
>
> Dear Prof. Blaha and Dr. Bhamu,
>
> Thank you Prof. Blaha for the valuable suggestion and I have followed all
> the steps as you have mentioned for the optimization. But still I have
> doubt when I am going to calculate the optimized lattice parameters from
> the optimized volume. The initial volume calculated using the lattice
> parameters before the volume optimization (values I have mentioned earlier)
> is 20805.429 Bohr^3. The scf file (before the volume optimization) shows
> the lattice parameters (LATT) and volume (infact this volume is the volume
> before inducing the mixing  into the 2*2*2 supercell) to be "a=18.508,
> b=39.835, c=40.199 Bohr; α=119.701◦, β=103.309◦, γ=90.0◦" and "24823.466
> Bohr^3", respectively. I am confused about the initial volume which one I
> should consider and why is this dissimiarity?
>
>
> --
> With regards
> Anupriya Nyayban
> Ph.D. Scholar
> Department of Physics
> NIT Silchar
>
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