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
>>
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