[Wien] regarding mixing parameter in hybrid calculations

[tran at theochem.tuwien.ac.at]

No

On Saturday 2018-08-04 16:22, Dr. K. C. Bhamu wrote:

>Date: Sat, 4 Aug 2018 16:22:20
>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: Re: [Wien] regarding mixing parameter in hybrid calculations
>
>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
>
>
>
>
>      _______________________________________________
>      Wien mailing list
>      Wien at 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
>
>
>
>