<div dir="auto"><div>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.)<div dir="auto"><br></div><div dir="auto">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.</div><div dir="auto"><br></div><div dir="auto">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.</div><div dir="auto"><br></div><div dir="auto">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.</div><div dir="auto"><br></div><div dir="auto">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.</div><div dir="auto"><br></div><div dir="auto">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.<br><br><div data-smartmail="gmail_signature" dir="auto">---<br>Professor Laurence Marks<br>"Research is to see what everybody else has seen, and to think what nobody else has thought", Albert Szent-Gyorgi<br><a href="http://www.numis.northwestern.edu">http://www.numis.northwestern.edu</a><br>Corrosion in 4D <a href="http://MURI4D.numis.northwestern.edu">http://MURI4D.numis.northwestern.edu</a><br>Partner of the CFW 100% gender equity project, <a href="http://www.cfw.org/100-percent">www.cfw.org/100-percent</a><br>Co-Editor, Acta Cryst A<br> </div></div><br><div class="gmail_extra"><br><div class="gmail_quote">On Jan 26, 2017 04:18, "Luis Ogando" <<a href="mailto:lcodacal@gmail.com">lcodacal@gmail.com</a>> wrote:<br type="attribution"><blockquote class="quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>Dear Prof. Marks,<br>
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Thank you very much for your answers ! I am pretty sure that your "intuition" will save a lot of computation time !<br>
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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.<br>
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<wbr> 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.<br>
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<wbr> My question is : in this case (regular SCF cycle and InP cells), would you change any of your previous answers ?<br>
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Thank you again !!<br>
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All the best,<br>
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Luis<br>
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<<a href="mailto:L-marks@northwestern.edu" target="_blank">L-marks@northwestern.edu</a>></span>:<br>
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<div class="gmail_quote"><span>On Wed, Jan 25, 2017 at 11:32 AM, Luis Ogando
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<div>Dear Prof. Marks (and Wien2k community),<br>
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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.<br>
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I have a system with:<br>
* 5 rings with C, H and N atoms<br>
* 100 atoms with P1 symmetry <br>
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I know that this is a very hard optimization problem, so I would like to kindly ask:<br>
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1) Do you believe that MSEC3a will work better than MSR1a in such a case ?<br>
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<div>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.</div>
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2) Do you recommend using -it, -vec2pratt and -noHinv options with run_lapw ?<br>
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<div>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
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3) Should I reduce TRUST to 0.5 (I am using LDA and experimental values for the initial atomic positions) ?<br>
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<div>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. </div>
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4) Should I use SLOW in case.inm ? <br>
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<div>See my answer to 1) </div>
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Many thanks in advance.<br>
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All the best,<br>
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Luis<br>
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<div dir="ltr"><span style="font-size:12.8px">Professor Laurence Marks</span><br>
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<div dir="ltr"><span style="font-size:12.8px">"Research is to see what everybody else has seen, and to think what nobody else has thought", </span><span style="font-size:12.8px">Albert Szent-Gyorgi</span><br>
<a href="http://www.numis.northwestern.edu" target="_blank">www.numis.northwestern.edu</a> ; <span style="font-size:12.8px">C<wbr>orrosion in 4D:
</span><a href="http://MURI4D.numis.northwestern.edu" style="font-size:12.8px" target="_blank">MURI4D.numis.northwestern.edu</a>
<div><span style="font-size:12.8px">Partner of the CFW 100% program for gender equity, </span><a href="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=" style="font-size:12.8px" target="_blank">www.cfw.org/100-percen<wbr>t</a></div>
<div>Co-Editor, Acta Cryst A</div>
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