[Wien] Electric Field -- is energy right?

[Laurence Marks]

Useful notes. One should only use the options for something like a surface,
and the method is a bit "Experimental" and not well documented. The next
time I look in a mirror I will tell the person who added the incomplete
"999" information output to improve that.

The forces should be correct, years ago they were checked as the energy
change of a proton/ion. I don't know of a way to check for a missing
constant in the energy.

---
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 Mar 7, 2017 22:15, "Gavin Abo" <gsabo at crimson.ua.edu> wrote:

> Not sure if it helps, but below are notes I have made on the electric
> field:
> ------------------------------------------------------------
> --------------------------------
> Use of the electric field seems somewhat undocumented.
>
> Reference the case.in0 section (7.1.3) in the WIEN2k usersguide [
> http://susi.theochem.tuwien.ac.at/reg_user/textbooks/usersguide.pdf
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__susi.theochem.tuwien.ac.at_reg-5Fuser_textbooks_usersguide.pdf&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=hunOVhWKc9GBCWcrWxIRS4S-Xrzt0_DzMiPlZfhp_Kc&e=>
> ].
>
> There seems to be 13 modes and 2 Fourier options to choose from.  To list
> the modes, add:
>
> -999 2
>
> on line 4 in the case.in0 file, then run in a terminal in the case
> directory:
>
> x lapw0
>
> It should output:
>
> Available E-field modes
> Mode  0 is Analytic triangular ramp
>
> Mode  1 is =0 if |z|<lambda, otherwise E*cos((z0-lambda)*pi2/(0.5-lambda))
>
> Mode  2 is =0 if |Z|<lambda, otherwise E*(1.D0-cos((z0-lambda)*pi2/(0.5-lambda)))
>
> Mode  3 is =0 if |z|<lambda, otherwise E*(1-cos((z0-lambda)*pi/(0.5-lambda)))*0.5D0
>
> Mode  4 is =E if |z|<lambda, otherwise E*(0.5D0-Z0)/(0.5d0-lambda)
>
> Mode  5 is =0 if |z|<lambda, otherwise E*(1.D0-(0.5D0-Z0)/(0.5d0-lambda))
>
> Mode  6 is Form from Lozovoi et al, J. Chem Phys, 115, 1661, 2001,
> normalized to max of 1
> Mode  7 is Form from Lozovoi et al, J. Chem Phys, 115, 1661,
> 2001
> Mode  8 is =Constant E
>
> Mode  9 is =0 if |z|<lambda, otherwise E
>
> Mode 10 is =E if |z|<lambda, otherwise E*((1-cos((z0-lambda)*pit/cut))*0.5D0)
>
> Mode 11 is Numerical Triangular ramp from E/2 to
> -E/2
> Mode 12 is Numerical Triangular ramp from 0 to
> -E
> Add 20 for finite Fourier series
> Add 40 for Fourier expansion within RMTs
>
> Note: The above list isn't fully displayed when x lapw0 is ran in w2web,
> so use a terminal instead of w2web.
>
> According to the post
>
> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2008-May/010928.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_pipermail_wien_2008-2DMay_010928.html&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=1Azt3QgtYKxnYQv7WdNzZXP74krK6hibZqO-aXocyt8&e=>
>
> run a typically scf cycle to convergence without the electric field (line
> 4 blank in case.in0).
>
> Then, add the electric field.  For example, if "Mode 8 is =Constant E" is
> chosen with an amplitude of 5 Ry, then line 4 of case.in0 would be
>
> 8000 5
>
> where Mode = IEFIELD/1000 = 8000/1000 = 8
>
> If a value of lambda of say 3 is specified such as for Mode 1, then add it
> as a third column value to line 4 of case.in0:
>
> 1000 5 3
>
> Then, run x lapw0 or another scf cycle for the electric field.
>
> I don't know if a supercell needs to be used for all or just some of the
> potentials.  Could try asking the mailing list.  Also, refer to the posts:
>
> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2011-June/014946.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_pipermail_wien_2011-2DJune_014946.html&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=_Rbm4Iu1zY3YBG7AOzhMYo3UfyT01Ji3v318ZWESNp8&e=>
> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2004-
> September/003549.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_pipermail_wien_2004-2DSeptember_003549.html&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=W7j7HOJhjXEIPGSNEPJ_l-2AGqkcZF0yogWBaNupYZU&e=>
> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2008-
> September/011449.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_pipermail_wien_2008-2DSeptember_011449.html&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=85n5Eq-7FCG0AZt-W2-JZnIcp1e2ilw93-FawCKED2s&e=>
> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2008-
> September/011340.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_pipermail_wien_2008-2DSeptember_011340.html&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=u4FFv8oeGkd943JodFfp2V0tq7nEuU5RcyGKPIYeikE&e=>
>
> E-field source code: SRC_lapw0/epot1.f
> ------------------------------------------------------------
> --------------------------------
>
> As a quick test only, I put "120 -0.50" in line 4 of TiC.in0 and ran x
> lapw0.  The output in TiC.scf0 suggests the 120 gives a triangular ramp
> electric field with 120 Fourier coefficients, and it also sets an amplitude
> of -0.5 Ry.  So I'm wondering if the behavior seen in the difference
> observed between structures A & B has anything to due with how the
> triangular ramps have been positioned in those two structures.
>
> username at computername:~/wiendata/TiC$ grep :EFIELD *.scf0
> :EFIELD       E-field of   -0.50000 Ry with  120 Fourier coefficients
> requested
> :EFIELD       Form is Analytic triangular ramp
>
> :EFIELD       Number of FC in E-field   8 , Largest   14
>
> On 3/7/2017 8:59 AM, Laurence Marks wrote:
>
> I probably should know/remember the answer to this question, but I don't.
>
> In lapw0 we can add an electric field, is the energy right or not?
>
> For reference, I have two different structures A & B and I want to compare
> the change in energy between the two in a field. The difference is opposite
> to what I expected, so either my expectation is wrong or an energy term is
> missing. For reference, I have added "120 -0.50" at the bottom of case.in0
> and I am minimizing the positions/forces (which I seem to remember were
> right but that does not prove that a constant is not missing). Uncharged
> unit cell.
>
>
> --
> 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-percent
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.cfw.org_100-2Dpercent&d=CwMD-g&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=eeKYEMnftGLp2ut0c9RNPvtayAX6L0w5gp9ebwewtSI&s=Nr4_h2YSvj7mBiMfRqW0WLUqZs68s-Wj4xIyvu9N7KE&e=>
> Co-Editor, Acta Cryst A
>
>
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