Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Messages - GJK

Pages: [1] 2 3 ... 14
First of all we sincerely thank you.

How to fix ghost atoms and boundary conditions for the functionalized ZGNR structure which is already given in as image file in attachment???

We want to compute the workfunction of functionalized ZGNR.

We have tutorial only for Silver work function.

Do we need to include ghost atoms or can we consider the chemical potential as work function???

That are two completely different things. Work function is in the energy required to remove an electron from the Fermi level and move it far from the surface to the vacuum level. If the vacuum level energy coincides with zero energy (which can be checked by computing the effective potential or Hartree difference potential), then work function is absolute value of the chemical potential. Otherwise, you have to measure the energy between the Fermi energy (chemical potential) and the vacuum level energy as given by the effective or Hartree difference potential.

Using ghost atoms might be required for more accurate description of wave function tails in the vacuum region, i.e., relatively-far from the surface, when using an LCAO basis set, because of the localized nature of the numerical atomic orbitals.

As per this reply we calculated the Hartree Difference potential and effective potential of ZGNR and functionalized ZGNR and obtained + 0.14 eV and -0.71 eV respectively.Whereas the effective potential came as -52 eV and -53 eV respectively.But we calculated without inclusion of ghost atoms.We took difference between this Hartree difference potential and Chemical potential which is the work function and obtained 5.24 eV for ZGNR.But the maximum reported value in litreature for graphene is 4.9 eV.

How and where to include the ghost atoms???
What should be the maximum vacuum padding to be fixed???
What boundary conditions to be employed for this kind of structure???

Also we have attached the Hartree difference potential calculated for ZGNR.
The formula for work function is W= -e(phi)-EF

1.Should we multiply the Hartree difference potential by e???
2.As you advised, we computed both Effective potential and Hartree difference potential but we are getting two different values as reflected by colour coding. What potential value we should subtract from Fermi Level(Chemical Potential)???

Because Effective potential is showing -52 eV whereas Hartree Difference Potential is showing +0.14 eV which value we should take for vacuum energy level???

Herby I have attached the effective potential for ZGNR. How to find the value of effective potential inorder to calculate the vacuum  level energy. Since, we are getting a 3-dimensional cube file.

How to calculate the workfunction for the functionalized graphene nanoribbon which is given in the attachment???


In the calculator we have option ATK_DFT and we use LDA.PZ single zeta polarized for our functionalized GNR structure and optimized the same. In result we obtained the chemical potential.can we consider chemical potential to be the work function???

Because we did optimization of the structure as a whole.Do we need to include ghost atoms or can we consider the chemical potential as work function???


I have read this tutorial.For graphene nanoribbon. We  are already defining the structure for GNR as described by QUANTUMATK.

In the tutorial for Ag work function there are parameters for vacuum padding ,thickness  etc.
How to fix ghost atoms in GNR?? Do we need to perform surface cleave as said for Silver in your tutorial???

We are already calculating chemical potentail for our functionalized system.Can we take that as work function?? If not then how to fix the ghost atom and is surface cleave parameters necessary for GNR???


Request the procedure for computing the work function of functionalized graphene nanoribbon..For silver we have but what are the parameters to be fixed if we are to compute workfunction of GNR.A detailed procedure could help us in this regard

Already we are calculating chemical potential during optimization process.Can we use that result as work function or not???

General Questions and Answers / Re: Band structure Energy
« on: June 1, 2019, 16:49 »

You mean above and below EF(which is normaized to zero) in the Bandstructure plot the energy values are plotted as E-EF in the y-axis???

General Questions and Answers / Re: Band structure Energy
« on: May 31, 2019, 16:38 »
What does "Energy Referenced to the Fermi Level means"-
1.Is it  Fermi level alone normalized to zero??

2.The other Energy values lying above and below the Fermi level are just E or is it E-EF???

Kindly clarify

General Questions and Answers / Re: Band structure Energy
« on: May 30, 2019, 12:21 »

But is the Fermi level alone is normalized to zero? The rest values in Y axis is only energy E and not E-Ef.

Am I correct?

General Questions and Answers / Re: Band structure Energy
« on: May 17, 2019, 11:59 »
Band structure for question 1

General Questions and Answers / Re: Band structure Energy
« on: May 17, 2019, 10:56 »
2. In the X-axis plot of band structure, we have the Brillouin zone route specified for each material. Is that the k points???

Because specifically if we draw E-k diagram do we need to replot the band structure or what ATK provides us user-friendly E Vs Brillouin zone route is the E-k plot??? Certain tutorials of yours also claim it as E-k plot. Your valuable reply is highly appreciated.


General Questions and Answers / Re: Band structure Energy
« on: May 17, 2019, 10:50 »

1. Once we generate band structure through our quantum ATK we get a plot between Energy  E and Brillouin zone route(attachment given). The Fermi level EF is normalized to zero. The y-axis says its energy E.The question is that -in the y-axis is it E-EF plot or just E with Fermi level alone being normalized to zero.


General Questions and Answers / Band structure Energy
« on: May 14, 2019, 09:23 »

1. We are getting bandstruture diagram appearing as Energy Vs Brillouin zone. What does that diagram signify in our software--Is it E-EF Vs Brillouin zone (or) E Vs Brillouin zone.

2. Is the Brillouin zone plotted in X axis and the k points are same or not???

Your reply is highly appreciated in advance.

General Questions and Answers / Graphene-reg
« on: January 16, 2018, 12:31 »
For graphene the first brillouin route is Gamma,M,K,Gamma

For ribbon it is denoted as Gamma,Z

In my system ZGNR the valid point symbols in ATK are shown as Y,X,Z,G
What does Y,X signify in ATK??? Z signify the K and G the gamma point

Should we use G,Z or Y,X,Z,G

Pages: [1] 2 3 ... 14