[Wien] regarding mixing parameter in hybrid calculations

[Dr. K. C. Bhamu]

Thanks Dr. Tran,



My mistake, the standard value is 0.25!!

Yes, I saw the link you provided (response was on my own queries).


What is advised there is:


"What you get from the optic calculation (the case.epsilon) file is only
the electronic part  (and not even the whole electronic part) of the
dielectric constant."

To get the ionic part of the static dielectric  constant you would need to
do the BERRYPI calculations to get Born effective charges tensors."



Do you have any previous experience on how much the properties may vary if
we avoid the "ionic part of the dielectric constant'?



Thanks and regards








On Sat, Aug 4, 2018 at 7:13 PM, <tran at theochem.tuwien.ac.at> wrote:

> Hi,
>
> First, the standard value is 0.25 and not 0.025.
>
> For the dielectric constant, there was alreday some explanations here:
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14936.html
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14875.html
>
> alpha_opt at V=V_exp means that the dielectric function (and alpha_opt)
> is calculated only at V_exp and then used for all other volumes.
> See also this:
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg15531.html
>
> No, it is not mandatory to do PBE calculation before YS-PBE0. Starting
> YS-PBE0 from PBE electron density (case.clmsum) may just help to reduce
> the number of SCF iterations with YS-PBE0.
>
> Of course it is possible to optimize lattice parameters with YS-PBE0.
> You just need to add the "-hf" option in the optimize.job file.
> What is not possible with YS-PBE0 is to optimize the position of
> atoms in the unit cell (because the forces are not implemented for
> YS-PBE0).
>
> FT
>
>
> On Saturday 2018-08-04 14:46, Dr. K. C. Bhamu wrote:
>
> Date: Sat, 4 Aug 2018 14:46:02
>> From: Dr. K. C. Bhamu <kcbhamu85 at gmail.com>
>> Reply-To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.
>> at>
>> To: A Mailing list for WIEN2k users <Wien at zeus.theochem.tuwien.ac.at>
>> Subject: [Wien] regarding mixing parameter in hybrid calculations
>>
>> Dear Dr. Tran,
>>
>> In the recent past, I did some calculations using YS-PBE0 for MgO and
>> results were well reproduced (wien2k Exercise).
>>
>> I just read your paper (J. Phys.: Condens. Matter 25 (2013)) and get to
>> know that we can control the mixing parameter using various ways.
>>
>> 1) Standard value (0.025)
>> 2) By fitting  (alpa_opt)
>> 3) alpa_opt (V=V_exp)
>>
>> I have queries for option 2 and 3 alpa:
>>
>> 2) If I am not wrong (after having a detailed search), the value of
>> dielectric constant used to get alpa_opt is the value of dielectric
>> constant from
>> Rel(epsilon) at energy 0.013610 eV, right?
>>
>> 3) How to get alpa_opt at V-V_exp?
>>
>>
>>
>>
>>
>> My next query is:
>>
>> It is reported in the Wien2k exercise that to do YS-PBE0 calculations we
>> need to do a simple PBE scf.  So if we really need to perform PBE
>> calculations before
>> going to YS-PBE0, I am wondering how to use YS-PBE0 to optimize the
>> lattice parameters and to get structural properties?
>>
>>
>> Could you please advice me on my concerns?
>>
>> * in above text "_" means an underscore.
>>
>>
>> regards
>>
>>
>>
>>
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