[Wien] proper k-points for Nd

Victor Zenou zanov at post.bgu.ac.il
Fri Jan 18 12:45:55 CET 2019


Dear ciao Gerhard I assumed ferromagnetic structure. I didn't try afm. I
got MMTOT=~16, while experiments show ~3.5. So I probably should try afm. By
the way, there is a way for me to skip that Nd calculations and still get
what I basically looking for, which enthalpy of formation. But now I'm very
interested to know what went wrong, also to avoid that in the future. Victor

‫בתאריך יום ו׳, 18 בינו׳ 2019 ב-10:40 מאת ‪Fecher, Gerhard‬‏ <‪
fecher at uni-mainz.de‬‏>:‬

> Dear Viktor,
> what magnetic order are you assuming at the start ?
>
> I remember that afm with Nd1 (0,0,0) up and Nd2 (1/3,2/3,1/4) dn was
> converging but there was always a small difference in the magnetic moments
> even with FSM
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von
> Laurence Marks [L-marks at northwestern.edu]
> Gesendet: Donnerstag, 17. Januar 2019 22:57
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] proper k-points for Nd
>
> Dear Viktor,
>
> Let me add something about large RMTs. I have noticed in the past that, in
> general,  the gradient at the RMT calculated from both sides (x RMTCheck)
> is very similar, e.g.
>
> Atom   1 O    | RMT Charge   0.489 Grad   0.690 | Step Charge  0.00136,
> 0.00000 Gradient   0.2655, -0.2655 O
>
> The last two numbers should sum to almost zero. However, with very large
> RMTs they can deviate from this, particularly when the gradient is small. I
> think this leads to anomalies at the RMT. (Peter would say that the
> linearization is breaking down with an inadequate basis set, or something
> similar.) Reducing the RMTs generally avoids this.
>
> While it is true that larger RMTs are "better" in terms of speed for a
> single iteration, slightly smaller RMTs which may take longer for a single
> iteration but are more stable so require fewer iterations can be nett
> faster. Speed is not the same as stability and convergence, and often they
> oppose each other. (Think about the tradeoff with condenser aperture size:
> smaller is more coherent but more drift...)
>
> N.B., are you really sure that the Nd distances are that large?
>
> On Thu, Jan 17, 2019 at 3:31 PM Peter Blaha <pblaha at theochem.tuwien.ac.at
> <mailto:pblaha at theochem.tuwien.ac.at>> wrote:
> 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> <mailto:
> 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
> >     http://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>
> >     <mailto: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> <mailto:
> 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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> --
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Gyorgi
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