# [Octopus-users] Static electric field

Sherif Tawfik shtawfic at aucegypt.edu
Tue Feb 23 18:37:56 WET 2010

```Hi Emily!

Thanks again. I'd like to show you my input file, and the results i got.
Here you are:
CalculationMode = gs
Units = eV_Angstrom

spacing = 0.25

CH = 1.2
%Coordinates
"C" |           0 |          0 |           0
"H" |  CH/sqrt(3) | CH/sqrt(3) |  CH/sqrt(3)
"H" | -CH/sqrt(3) |-CH/sqrt(3) |  CH/sqrt(3)
"H" |  CH/sqrt(3) |-CH/sqrt(3) | -CH/sqrt(3)
"H" | -CH/sqrt(3) | CH/sqrt(3) | -CH/sqrt(3)
%

Output = potential
OutputHow = plane_y + plane_x + plane_z + axis_x + axis_y + axis_z

%StaticElectricField
0 | 0 | 1
%

Then, I got this for vks (x=y=0):
#         z                     Re                     Im
-4.00000000000000E+000 -4.19230091502157E+000  0.00000000000000E+000
-3.75000000000000E+000 -4.18220119808857E+000  0.00000000000000E+000
-3.50000000000000E+000 -4.16325365969853E+000  0.00000000000000E+000
-3.25000000000000E+000 -4.16871952117951E+000  0.00000000000000E+000
-3.00000000000000E+000 -4.22201527374675E+000  0.00000000000000E+000
-2.75000000000000E+000 -4.34785759303653E+000  0.00000000000000E+000
-2.50000000000000E+000 -4.57718242334871E+000  0.00000000000000E+000
-2.25000000000000E+000 -4.95309736808654E+000  0.00000000000000E+000
-2.00000000000000E+000 -5.54164879094784E+000  0.00000000000000E+000
-1.75000000000000E+000 -6.45422281457328E+000  0.00000000000000E+000
-1.50000000000000E+000 -7.90212098547652E+000  0.00000000000000E+000
-1.25000000000000E+000 -1.03453221534189E+001  0.00000000000000E+000
-1.00000000000000E+000 -1.49903103291576E+001  0.00000000000000E+000
-7.50000000000000E-001 -2.56449027580626E+001  0.00000000000000E+000
-5.00000000000000E-001 -4.49276823917520E+001  0.00000000000000E+000
-2.50000000000000E-001  2.28303782392187E+000  0.00000000000000E+000
0.00000000000000E+000  1.41409996400464E+001  0.00000000000000E+000
2.50000000000000E-001  2.57784824968849E+000  0.00000000000000E+000
5.00000000000000E-001 -4.43872292818089E+001  0.00000000000000E+000
7.50000000000000E-001 -2.49733689950766E+001  0.00000000000000E+000
1.00000000000000E+000 -1.40569691078456E+001  0.00000000000000E+000
1.25000000000000E+000 -8.95059202697836E+000  0.00000000000000E+000
1.50000000000000E+000 -5.89519442843200E+000  0.00000000000000E+000
1.75000000000000E+000 -3.76192022805158E+000  0.00000000000000E+000
2.00000000000000E+000 -2.15244999338650E+000  0.00000000000000E+000
2.25000000000000E+000 -8.90445817070239E-001  0.00000000000000E+000
2.50000000000000E+000  1.21431093596337E-001  0.00000000000000E+000
2.75000000000000E+000  9.47241504889888E-001  0.00000000000000E+000
3.00000000000000E+000  1.63341612890374E+000  0.00000000000000E+000
3.25000000000000E+000  2.21548567169309E+000  0.00000000000000E+000
3.50000000000000E+000  2.72188819650366E+000  0.00000000000000E+000
3.75000000000000E+000  3.17735377156892E+000  0.00000000000000E+000
4.00000000000000E+000  3.60979283622384E+000  0.00000000000000E+000

but it is not a straightline at all.. which is confusing. And even if i get
the straightline, and hence the stope, how can i know that the number "1" i
enetered in the static electric field section is actually 1 Volts/Ang?

Really sorry if this sounds silly :) Please bear with me :)

Yours,
Sherif

On Tue, Feb 23, 2010 at 8:21 PM, Emily <listemily at eml.cc> wrote:

> I don't know.  I didn't work on the code, so I don't know what M_ONE and
> M_TWO are.  But you can test your guess according to the instructions in
> my previous e-mail.  Good luck!
>
> :) Emily
>
>
> ----- Original message -----
> From: "Sherif Tawfik" <shtawfic at aucegypt.edu>
> To: "Emily" <listemily at eml.cc>
> Date: Tue, 23 Feb 2010 19:57:43 +0200
> Subject: Re: [Octopus-users] Static electric field
>
> In the code, i realized that octopus multiplies the static values by the
> factor M_ONE/(M_TWO*P_Ry) according to the line:
>    u%energy%factor = M_ONE/(M_TWO*P_Ry)   ! 1 a.u. = 27.2 eV
>
> This means that if i want to enter 1V/Ang on the z axis, i should enter
>
> %StaticElectricField
>    0 | 0 |  1/e
> %
>
> where e is the charge in eV. Right?
>
> On Tue, Feb 23, 2010 at 7:27 PM, Sherif Tawfik
> <shtawfic at aucegypt.edu>wrote:
>
> > Hi Emily!
> >
> > I took your advise, and I am running a gs run to out the potential. I
> > octopus to output plane and axis files. The silly question: how can I use
> > those files (for the components of the KS potential) to obtain the units
> of
> > the static electric field?
> >
> >
> > On Tue, Feb 23, 2010 at 7:06 PM, Emily <listemily at eml.cc> wrote:
> >
> >> Hi Sherif,
> >>
> >> I did once figure out the units on the electric field, but I don't quite
> >> recall what they were.  It was reasonable and consistent, but I think I
> >> was using atomic units anyway.
> >>
> >> You can verify most rigorously by applying a test field and then
> >> plotting the potential.  You can use  Output=potential to see the
> >> different parts of the potential.
> >>
> >>
> http://www.tddft.org/programs/octopus/doc/3.2.0/html/vars/Output.html#Output
> >>
> >> The changes page:
> >> http://www.tddft.org/programs/octopus/wiki/index.php/Changes doesn't
> >> list any change in the implementation of the electric field between
> >> those two versions.  But maybe one of the developers will write back and
> >> verify that for you.
> >>
> >> :) Emily
> >>
> >> ----- Original message -----
> >> From: "Sherif Tawfik" <shtawfic at aucegypt.edu>
> >> To: "Emily" <listemily at eml.cc>
> >> Cc: "octopus-users" <octopus-users at tddft.org>
> >> Date: Tue, 23 Feb 2010 18:49:29 +0200
> >> Subject: Re: [Octopus-users] Static electric field
> >>
> >> Thanks a lot Emily!
> >>
> >> So, the units are Volts/Angstroms (in case Angstrom units are used)? And
> >> is
> >> there a difference between the implementation in octopus 3.1.0 and 3.2?
> >>
> >> On Tue, Feb 23, 2010 at 6:31 PM, Emily <listemily at eml.cc> wrote:
> >>
> >> > Yes, you can:
> >> >
> >> > from
> >> >
> >> >
> >>
> http://www.tddft.org/programs/octopus/doc/3.2.0/html/vars/Hamiltonian.html#StaticElectricField
> >> >
> >> > StaticElectricField
> >> > Section: Hamiltonian
> >> > Type: block
> >> >
> >> > A static constant electric field may be added to the usual
> Hamiltonian,
> >> > by setting the block StaticElectricField. The three possible
> components
> >> > of the block (which should only have one line) are the three
> components
> >> > of the electric field vector. WARNING: This should not be used in a
> >> > periodic direction.
> >> >
> >> > ----- Original message -----
> >> > From: "Sherif Tawfik" <shtawfic at aucegypt.edu>
> >> > To: "octopus-users" <octopus-users at tddft.org>
> >> > Date: Tue, 23 Feb 2010 17:41:53 +0200
> >> > Subject: [Octopus-users] Static electric field
> >> >
> >> > Hi all!
> >> >
> >> > How can I apply a static electric field on a structure, say a field of
> 1
> >> > Volts/Angstrom?
> >> >
> >> > Thanks a lot in advance!
> >> >
> >> > Sherif Tawfik
> >> >
> >>
> >
> >
>
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