Topics

1

General Questions and Answers / Band decomposed charge density

« on: April 19, 2017, 07:48 »

Hi,
I want to calculate the band decomposed charge density. For example, if I simulate silicon bulk using ATK-DFT then after that I want to calculate electron density (or charge density) in each valley of silicon (Delta and Gamma). I have checked this link http://quantumwise.com/forum/index.php?topic=1356.0 . But that is relevant for DeviceConfiguration. I have a BulkConfiguration. Is there anything similar for the bulk configuration?

 Also in the second comment (from Zh)
"The concept of the partial charge density of a given band or eigenvalue is basically the same as the local density of states.
http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.localdevicedensityofstates.html
The summing up the the local density of states for the eigenvalues at a specified band will give the band-decomposed partial charge density."
don't you think that just summing up ldos won't work in the conduction band. One has to sum up ldos x fermi function, no?

2

General Questions and Answers / Plotting pseudopotential potential

« on: January 19, 2017, 06:15 »

I want to plot pseudopotential contribution to the effective potential. The method ExternalPotential returns zero at all grid points. According to the background information it should be the part of external potential.

How do I get this contribution?

3

General Questions and Answers / MGGA formulation

« on: November 23, 2016, 16:23 »

In the original paper from Tran and Blaha, they use sqrt(5/12) factor. But QuantumWise is using sqrt(4/12) factor in their formulation http://docs.quantumwise.com/tutorials/inas_2d_mgga/inas_2d_mgga.html.
Which is the implemented version?

4

General Questions and Answers / negative DOS below the valence band

« on: May 19, 2016, 12:35 »

Strangely in Ge (or in Si) I see that the DOS projected onto p-orbitals is negative much below the valence band of Ge(or Si). What could be the reason for it?

5

General Questions and Answers / Ghost atoms, relaxation, workfunction

« on: May 13, 2016, 08:02 »

Hi,

I am getting the problems in relaxation when I include the ghost atoms. so,

How accurate the surface relaxation without ghost atoms?
And also how accurate the Workfunction calculations without ghost atoms?

Also, without ghost atoms, is it expected that with the basis set the workfunction of a metal changes significantly?

6

General Questions and Answers / Formtion Energy Tutorial Source code

« on: April 30, 2016, 10:13 »

Hi,
Is it possible to share the source code of the GaAs and MgO formation energy / cohesive energy tutorial?

7

General Questions and Answers / Chemical potential for the surface energy calculations

« on: April 23, 2016, 11:10 »

I  want to calculate the surface energies in a slab simulations. I am referring to this paper  http://dx.doi.org/10.1063/1.4761994 (Figure 2) which uses ATK + Thermodynamics to relate the chemical potential to the surface energy. I am confused with the use of chemical potential there. It corresponds to the Rhodium reservoir. If I simulate the Rhodium bulk in Quantumwise and calculate the chemical potential using the ChemicalPotential function, and the same for the Silicon, then is this ChemicalPotential corresponds to what paper refers to, an energy for the Rhodium reservoir?
The ChemicalPotential what ATK returns is actually a Fermi level.

8

General Questions and Answers / Vacuum Region and Density Mesh Cutoff

« on: April 8, 2016, 12:59 »

Hi,

Is there any relation between the density mesh cutoff and the length of vacuum padding in a slab simulation?
I mean in two calculations, the one with 10A of vacuum and the other with 50A, do I need to increase the density mesh cutoff for the latter one?

9

General Questions and Answers / LOCPOT 1D projector bug

« on: March 10, 2016, 12:20 »

Hi, I find that the 1D projector LOCPOT is calculated wrongly. I used the script here, https://github.com/compphys/ase_tools/blob/master/scripts/vtotav.py
which gives the correct value of the workfunction. The I precisely suspect the factor 4 that is being divided unnecessarily, can you please check this.

10

General Questions and Answers / Bug in labfloor update

« on: March 7, 2016, 07:58 »

There is a bug in the labfloor update. The labfloor is not being updated is some files are added in a subfolder. I guess this happens when a new folder is created while vnl is opened.

11

General Questions and Answers / Ge GGA+U

« on: February 2, 2016, 13:57 »

Hi,
I am trying to obtain the results published here doi:10.1016/j.commatsci.2015.10.023 for GGA+U calculations on Ge.
I do not obtain the convergence for the negative values of Up.  I have attached the .py file. Am I missing something?

12

General Questions and Answers / Electron Difference Density MGGA for NiGe

« on: January 4, 2016, 01:35 »

Hi,

I am doing the MGGA study on NiGe (from database).  A NiGe slab is simulated with GGA(blue) and MGGA(green) and then macroscopic average of the electron difference density is plotted.  A significant EDD can be seen at the edges of the slab, but in GGA and MGGA, signs are opposite.  The MGGA c parameter is set to be 0.97. Is MGGA reliable then? I am attaching the .py file of the simulations.

13

General Questions and Answers / spikes in effective potential in slab simulations using MGGA

« on: December 16, 2015, 16:21 »

Hi,
In the effective potential, why the spikes are observed near the edges of the slab (vacuum/material interface) with MGGA functional. Is it fine to observe such spikes?

14

General Questions and Answers / Printing information about basisSet

« on: December 16, 2015, 06:54 »

Hi, I want to print the information about the basis set used in an older .nc file. I tried nlprint(bulk_configuration.calculator().basisSet()) or nlprint(bulk_configuration) but its of no use.  Amy way how to do in? More specifically I want to know which predefined basis set(HGH tier4, HGH tier8 or doublezetapolarized) was used.

15

General Questions and Answers / NiGe PDOS

« on: December 14, 2015, 00:41 »

Hi, I am testing the basis set on NiGe. I using the http://journals.aps.org/prb/pdf/10.1103/PhysRevB.75.085326 (Fig 3) to check for the PDOS. With DoubleZetaDoublePolarized basis I am not getting the PDOS onto Ge as resembling to the paper. The PDOS on Ni are resembling. But in the HGH Tier4 basis, even PDOS onto Ni (for s and p orbitals) are different from the paper.
1. Is it expected to see a significant difference in the PDOS with different basis sets?
2. Is it wise to compare the PDOS results of VAPS code(paper) and ATK?
3. The d-orbital in Ge is 3d or 4d?

Density mesh cutoff is set quite high at 425 Hartree. The Kmesh was 16x16x24, and for dos  calculations 25x25x25.