Dear Prof. Marks, Thank you very much for the explanations. They will be useful now and in the future. My last query (I promise !!): Could you, please, clarify the meaning of the last two columns in a :MIX line ? For example :

:MIX : MSE1 REGULARIZATION: 4.93E-06 GREED: 0.437 Newton 1.00 1.14 Thank you again ! All the best, Luis 2017-01-26 11:01 GMT-02:00 Laurence Marks <l-ma...@northwestern.edu>: > A clarification on some terms/types. For certain -eece and probably also > +U can stop at what should be called "traps". This is when :DIS and the > plane waves (:PLA) are self-consistent, but :MV is not. You can also have a > trap where :DIS is small but :PLA is not, and if you start from a converged > density but the forces are large. The latest mixer does a better job of > escaping these traps. I would not be surprised to find that there are > published results which are really traps. (Not just with Wien2k, with other > DFT codes as well.) > > Local minima are "real" and "right". Wien2k (and most other codes) will > stop at local minima, only a few search for the global minimum. For certain > one can have local minima for spin states; it is not impossible to have > local minima for atomic positions. MSR1(a) can escape from small traps, > i.e. ones which are only present for a small range of densities/positions. > Sometimes small traps are due to noise in the algorithms. > > Your InP case could find a local minimum, or a trap. Traps you can check > by looking to see if terms in addition to :DIS are converged. > > mBJ is a special case that I don't understand -- I have not worked with it > enough to know if it has traps. I also don't know if the forces with mBJ > can be trusted. From some simple tests I did I suspect that they can't, but > I am not certain. > > To escape a trap or a small local minimum you don't want to add SLOW, > decrease the GREED etc. -- use the larger default parameters. > > To escape true local minima (spin or positions) you have to change to a > new starting point that is outside the radius of convergence (in > spin/position/density space) of your earlier calculation. There are some > emails on the list about changing spin states by hand. > > --- > 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 > Corrosion in 4D http://MURI4D.numis.northwestern.edu > Partner of the CFW 100% gender equity project, www.cfw.org/100-percent > Co-Editor, Acta Cryst A > > > > On Jan 26, 2017 04:18, "Luis Ogando" <lcoda...@gmail.com> wrote: > > Dear Prof. Marks, > > Thank you very much for your answers ! I am pretty sure that your > "intuition" will save a lot of computation time ! > Just one last question: I have another system , a supercell formed by > 15 InP zinc blend cells along [111] (hexagonal representation of the cubic > lattice) and 3 InP wurtzite cells. They are aligned along the hexagonal "c" > axis. > Comparing the gaps of the respective > bulks and this supercell (same calculation parameters) , I believe that the > SCF cycle (here, it is not a lattice optimization) stopped at a local > minimum. > My question is : in this case > (regular SCF cycle and InP cells), would you change any of your previous > answers ? > Thank you again !! > All the best, > Luis > > > 2017-01-25 17:56 GMT-02:00 Laurence Marks <l-ma...@northwestern.edu>: > >> Inlined is my intuition, which does not have to be completely right. >> >> On Wed, Jan 25, 2017 at 11:32 AM, Luis Ogando <lcoda...@gmail.com> wrote: >> >>> Dear Prof. Marks (and Wien2k community), >>> >>> After a recent discussion about "difficult" optimizations in this >>> mailing list (subject: "Mixer surprise when using PBE0 hybrid on-site >>> functional"), I would like ask you for an advice. >>> I have a system with: >>> * 5 rings with C, H and N atoms >>> * 100 atoms with P1 symmetry >>> * the rings are out of a plane >>> * vacuum along y and z >>> I know that this is a very hard optimization problem, so I would like >>> to kindly ask: >>> >>> 1) Do you believe that MSEC3a will work better than MSR1a in such a case >>> ? >>> >> >> I would switch to MSEC3a, use SLOW or reduce the GREED to 0.1 only if you >> see indications of problems. If the system is a decent insulator and the >> experimental positions are quite good you may have no problems. At the end >> I would switch back to MSR1a certainly for a system with OH as the >> positions of the hydrogens can be quite soft. It can take quite some time >> to get the rotations of the OH bond distance right as Wien2k uses cartesian >> coordinates not polars. Which of the 3 is best -- I am not sure. >> >>> >>> 2) Do you recommend using -it, -vec2pratt and -noHinv options with >>> run_lapw ? >>> >> >> I use -it -noHinv -vec2pratt. Sometimes you need to do an occasional full >> diagonalization (touch .fulldiag) as the iterative method is less stable >> (it adds a little noise). In my personal version I have added back the old >> -itn option so this is done automatically every few steps. >> >>> >>> 3) Should I reduce TRUST to 0.5 (I am using LDA and experimental values >>> for the initial atomic positions) ? >>> >> >> Probably not. TRUST 0.5 would be if it is taking much too large steps >> which tends (in my experience) to occur more with soft electronic modes >> such as one has with d and f electrons. >> >>> >>> 4) Should I use SLOW in case.inm ? >>> >> >> See my answer to 1) >> >>> >>> Many thanks in advance. >>> All the best, >>> Luis >>> >>> >> >> >> -- >> 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 ; Corrosion in 4D: >> MURI4D.numis.northwestern.edu >> Partner of the CFW 100% program for gender equity, www.cfw.org/100-percen >> t >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.cfw.org_100-2Dpercent&d=CwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=MNscdaGYE15HljeOPwtzDZH4S_JeFNBLtGtQWhVb-FY&s=kL1N7z6QnaXOzYazrQU6rH7eGamLhLbu0ncgZ2Hfz0E&e=> >> Co-Editor, Acta Cryst A >> >> _______________________________________________ >> Wien mailing list >> Wien@zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_mailman_listinfo_wien&d=CwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=MNscdaGYE15HljeOPwtzDZH4S_JeFNBLtGtQWhVb-FY&s=UDSAKya4XEowVr79jb00mjlqKhzg84E5l-IbK3bng8c&e=> >> SEARCH the MAILING-LIST at: http://www.mail-archive.com/wi >> e...@zeus.theochem.tuwien.ac.at/index.html >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_index.html&d=CwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=MNscdaGYE15HljeOPwtzDZH4S_JeFNBLtGtQWhVb-FY&s=iutaZBD8d3Ad8lUmlUTPnDkvBCtab7ay4LhoDtLRwqY&e=> >> >> > > > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: http://www.mail-archive.com/ > wien@zeus.theochem.tuwien.ac.at/index.html > >

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