[Wien] proper k-points for Nd
Victor Zenou
zanov at post.bgu.ac.il
Fri Jan 18 10:52:29 CET 2019
Thanks Peter The calculation was terminated for me when energy convergence
was achieved. As a default I used 240 instead of 40 cycles. I'm repeating
the few of these calculations with charge convergence 0.001. When I get
sense of it, I will try HDLOs as LDM suggested. For all phases including
Al, having the lowest RMT, I used RMT*Kmax=7. For Ti I used 7.5 and for Nd
I used 8.5, as 7/2.3~7.5/2.5~8.5/2.7.
Why I choose so large RMT for Nd? I just followed the recommendations
appearing in Wien2k website (How to select RMT radii): In order to make the
calculations as fast as possible, choose the radii as large as possible,
but consider possible structural changes ….
Also: "atoms with d (f) states may be 20 (30)% larger" …..
I have to mention that in the past I never use RMT larger than 2.5. But now
as I have 6-7 phases, I wanted to expedite my calculations.
Victor
בתאריך יום ה׳, 17 בינו׳ 2019 ב-23:31 מאת Peter Blaha <
pblaha at theochem.tuwien.ac.at>:
> RMTs: Make sure that you choose RMTs, which can be used in all
> elemental solids, but the same should also be used in your compound.
>
> Yes, you can use very large RMTs if you follow the recommendations
> during init_lapw:
> Use HDLOs for f and (as L.Marks mentioned) probably d.
> Use lvns=6 (or 8) in case.in1
>
> For a difficult system (and Nd with partially occupied 5f electrons is
> definitely a difficult systems), scf convergence can be more difficult.
> Thus, as mentioned before, use both -ec and -cc (at least 0.001;
> eventually a better cc is difficult to reach. Often you may need MORE
> than the default max of 40 scf cycles. So when runsp_lapw stops, make
> sure it does not stop beucause of the 40 it limits.
> Clearly, your energies with :dis=0.2 are wrong.
>
> For the compound but also the elements, make sure to use "consistent
> RKMAX" values.
> If you use: Al Ti Nd (2.3,2.5,2.7) and for your compound you use
> RKMAX=8, than Al should be done with RKMAX=8, Ti with RKmax=8*2.5/2.3,
> Nd with 8*2.7/2.3
>
> Am 17.01.2019 um 21:19 schrieb Victor Zenou:
> > Dear Lauri
> > Thanks for your answer
> > I used only energy convergence criteria (10^-4). Still the charge
> > convergence was between 0.006 and 0.2 e.
> > The nearest neighbor distance is 6.856 a.u, I used RMT=2.7 a.u., summed
> > to 5.4 which is much lower than 6.856. Usually large RMT is preferred
> > to make the calculations as fast as possible. I plan to check a phases
> > in Al-Ti-Nd and I chose RMT equal to 2.3, 2.5 and 2.7 respectively.
> > Victor
> >
> >
> >
> > בתאריך יום ה׳, 17 בינו׳ 2019 ב-11:16 מאת Laurence Marks
> > <L-marks at northwestern.edu <mailto:L-marks at northwestern.edu>>:
> >
> > With such large RMT you certainly need HDLO for Nd, perhaps both d &
> > f. I would not want to use such large RMTs.
> >
> > Have you checked that the charge convergence is good?
> >
> > _____
> > Professor Laurence Marks
> > "Research is to see what everybody else has seen, and to think what
> > nobody else has thought", Albert Szent-Gyorgi
> > www.numis.northwestern.edu <http://www.numis.northwestern.edu>
> >
> > On Thu, Jan 17, 2019, 03:04 Victor Zenou <zanov at post.bgu.ac.il
> > <mailto:zanov at post.bgu.ac.il> wrote:
> >
> > Hi
> > Here is updated question:
> >
> > Dear Wien2k users
> >
> > I'm using wien2k version 17.1 installed on Ubunto 18.04.
> >
> > I need to calculate the enthalpy of formation of few
> > intermetallic phases that include Nd. For that element I used
> > RMT=2.7 a.u. and RMT*Kmax=8.5 for spin-polarization calculations
> > via GGA-PBE. I didn't try spin-orbit coupling. Yet.
> >
> > The first stage is to choose proper k-points, which will give
> > accurate results (I used 1x10^-4 Ryd for energy convergence) on
> > one hand, but on the other hand won't be expensive in terms of
> > computing time.
> >
> > I noticed that there are large energy fluctuations (1x10^-2 Ryd;
> > which are 2 order of magnitude higher than the energy accuracy
> > (defined by convergence criterion), even when I went to 15,000
> > k-points. Here is a list of energy as function of k-points:
> >
> > K-points IBZ E [Ryd]
> >
> > 100 8 -77040.4692
> >
> > 500 38 -77040.4780
> >
> > 1000 81 -77040.5062
> >
> > 2000 120 -77040.5061
> >
> > 3000 208 -77040.4391
> >
> > 4000 244 -77040.4699
> >
> > 5000 280 -77040.4878
> >
> > 7500 455 -77040.4707
> >
> > 10000 540 -77040.4881
> >
> > 15000 840 -77040.4694
> >
> > I would be happy to get an idea what could have gone wrong.
> >
> > Best regards, Victor
> >
> >
> >
> > בתאריך יום ד׳, 16 בינו׳ 2019 ב-13:59 מאת Victor Zenou
> > <zanov at post.bgu.ac.il <mailto:zanov at post.bgu.ac.il>>:
> >
> > Dear Wien2k users
> >
> > I'm using wien2k version 17.1 installed on Ubunto 18.04.
> >
> > As a part of investigation of intermetallic phases in
> > Al-Ti-Nd system, I need to calculate the enthalpy of
> > formation of few phases in that system. For that purpose, I
> > start calculating enthalpy (equal to energy at 0K) for each
> > element and phase at their optimal relaxed state. I used
> > spin-polarization calculations. (GGA-PBE) As advised in
> > Wien2k website I used the same RMT for each elements: 2.3,
> > 2.5 and 2.7 a.u. for Al, Ti and Nd, respectively. Also
> > proper RMT*Kmax (7.5 to Ti, 8.5 to Nd and 7.0 for the rest).
> >
> > The first stage is to choose proper k-points, which give you
> > accurate results (I used 1x10^-4 Ryd for energy convergence)
> > on one hand, but also some save computing time.
> >
> > The calculation for all elements and phases went OK, but Nd.
> > From certain k-points the energy fluctuated between 2 values
> > (differed by 1x10^-2). Attach a list of energy as function
> > of k-points:
> >
> > K-pointsIBZ E [Ryd]
> >
> > 1008-77040.4692
> >
> > 50038-77040.4780
> >
> > 100081-77040.5062
> >
> > 2000120-77040.5061
> >
> > 3000208-77040.4391
> >
> > 4000244-77040.4699
> >
> > 5000280-77040.4878
> >
> > 7500455-77040.4707
> >
> > 10000540-77040.4881
> >
> > 15000840-77040.4694
> >
> > I tried to get smart and did volume optimization using 4000
> > k-points, later 5000 k-points. I got strange results.
> >
> > I would be happy to get an idea what could have gone wrong.
> >
> > I didn't try spin-orbit coupling
> >
> > Best regards, Victor
> >
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>
> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
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