[Wien] Question about mBJ calculation

[David]

Thank you very much for your response,
I will follow your suggestion and run the case with MSEC1 just to make sure.
I will report my results later

Once again Thank you all for the help.

David G.

Department of Physics
California State University - Los Angeles




On 01/09/2011 11:40 AM, tran at theochem.tuwien.ac.at wrote:
> Dear David,
>
> 0.4 is probably large enough such that pseudo-convergence should not
> happen. Nevertheless, if you want to be sure that it's ok, you can
> restart the calculation (after having done save_lapw) with the default
> mixing parameters in case.inm (MSEC1 with 0.2).
>
> F. Tran
>
> On Sun, 9 Jan 2011, David wrote:
>
>> Professo Blaha,
>>
>> Thank you very much for your reply. Since the beginning of my calculation I've
>> been taking care of the mixing factor as you recommended. Now the calculation
>> seems to be approaching to convergence.
>>
>> However I'm a little concerned now about what you call "pseudo-convergence"
>> how can I evaluate if my calculation came to a full convergence or a
>> pseudo-convergence?
>>
>> By the way the mixing factor I'm using right now is 0.4 with the PRATT mixing
>> scheme, is this such a small mixing factor that could lead to
>> pseudo-convergence?
>>
>> Thank you very much for you help Dr. Blaha.
>>
>> David Guzman
>> Department of Physics
>> California State University - Los Angeles
>>
>> On 01/09/2011 01:16 AM, Peter Blaha wrote:
>>> Convergence of mBJ calculations is sometimes a bit tricky since not only the
>>> charge density but also the kinitic energy density (or the "vresp"-files)
>>> determine the potential.
>>>
>>> The recommended way is to start out with a PRATT mixing (with eg. 0.2)
>>> and once the :DIS has settled a bit (decreased from the initially big
>>> values, but then not changing much, usually after ~10 iterations) one can
>>> graduadely increase the mixing factor (to eg. 0.3 and 0.4). Maybe
>>> :DIS increases a little, but as long as there are no oszillations in ENE or
>>> ::GAP this is fine.
>>> Eventually, one may intermediately "save" the calculations (to have a
>>> restarting point) and continue with MSEC1, since once the vresp-files are
>>> partially converged, density-mixing as done with MSEC1 should be fine.
>>> Please be aware, that in mBJ-calculations not only the density (clmsum) is
>>> mixed, but that the mixing-factor in case.inm also mixes the
>>> exchange-potential in lapw0. Thus, there is a danger of "pseudo-convergence"
>>> when the mixing factor is too small.
>>>
>>> Am 09.01.2011 00:31, schrieb David:
>>>> Dear Professor Blaha and Wien users,
>>>>
>>>> I'm running mBJ calculations for CuZrTiO5, spin-polarized, it has 16
>>>> atoms in the unit cell, and im running 300 k-points. My ultimate goal is
>>>> to get the band structure of this crystal.
>>>>
>>>> I haven't got any problems regarding code errors, in fact up to now
>>>> everything has run very smooth. My question though is the following: the
>>>> has has run 58 cycles now and the charge distance does not seem to
>>>> reduce significantly, in fact for the first 45 cycles or so it reduced
>>>> very slow, but now it's going up again, I was wondering if this is a
>>>> common behaviour? Also I was wondering if there is any way I can make it
>>>> converge faster, I know this is a large calculation, but may be some of
>>>> you guys have suggestions.
>>>>
>>>> Some details about my calculation:
>>>>
>>>> 1. I run a regular spin-polarized scf cycle using the MSEC1 with a
>>>> mixing factor of 0.2 and it converged in 18 cycles (convergence criteria
>>>> was charge: 0.00001 e)
>>>>
>>>> 2. I followed the steps for mBJ calculations from the manual, I used
>>>> PRATT with a mixing factor of 0.2 and the convergence criteria is
>>>> charge: 0.00001 e
>>>>
>>>> 3. Attached are the case.struct and case.inst if it helps
>>>>
>>>> Please if you required any other information in order for me to get some
>>>> help, I can send it
>>>>
>>>> Thank you very much
>>>>
>>>> David Guzman
>>>> Department of Physics
>>>> California State University - Los Angeles
>>>>
>>>>
>>>>
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