Topics

1

General Questions and Answers / Density mesh cut-off for mgga

« on: December 8, 2017, 06:54 »

Hello,
I had analysed optical spectrum for phosphorene using mgga with two different values of density mesh cut-off (60 and 90 hartree) keeping all other values same for both the cases. The results had huge difference.
What value should we keep for cut-off for the optimum results and how do we decide for it?

2

General Questions and Answers / Refractive index

« on: October 14, 2017, 11:35 »

Hi sir,

What is refractive index? what is the significance of it and how can we explain the graph of refractive index obtained from VNL-ATK?

Thanks

3

General Questions and Answers / Doubt regarding Bandgap

« on: October 12, 2017, 11:43 »

Hello Sir,
With reference to paper "DOI: 10.1039/C7CP03960C", I tried calculating the band gap of the blue phosphorene and MoSe2 after interfacing them at the optimized interlayer distance of 3.8A.
I had tried with many combinations (SG15, FHI) and with strict mesh cut-offs but I was getting the 'indirect Band gap' unlike what the paper mentions of getting the 'direct band gap'.
Surprisingly  I tried with a different brillouin route (default - 'G, Z') and was getting a 'direct band gap' of 1.45eV (paper mentions 1.1eV).
My doubt is whether band gap depends on the brillouin route and if yes then what route should be selected for the reliable results?

4

General Questions and Answers / Creating stanene

« on: October 6, 2017, 19:48 »

Hello sir,
How can we create a unit cell of stanene? Is it possible to create using the same procedure as for silicene, as in one of the tutorials? If yes , then does it too requires few times perturbation as in silicene?

5

General Questions and Answers / MoS2 bandgap

« on: September 28, 2017, 19:20 »

Hello sir,
I have calculated the bandstructure of monolayer MoS2  using MGGA with basis set Tier 3 for both sulphur and Molybdenum  (pseudopotential- HGH[6] for sulphur and HGH[14] for molybdenum) and getting 1.87 eV band gap.

But when we change the Tier for molybdenum (Tier 4) we got the band gap of 1.79eV .

Please tell me how to select a Tier as basis set in MGGA method.

6

General Questions and Answers / Optical properties

« on: September 27, 2017, 12:53 »

Hello,
I tried to analyse optical spectrum using both exchange correlation 'GGA' & 'MGGA'.
Both results are totally different and GGA is converging fast as compared to MGGA.
Which of the results are reliable - 'GGA' or 'MGGA'?

7

General Questions and Answers / CFA-MoS2 monolayer

« on: September 21, 2017, 19:05 »

Dear users,
I am trying to interface Co2FeAl  (Heusler alloy) with MoS2 using the interface tool. The problem being faced is that the interatomic displacement option in the 'Shift Surface' parameter is not active and in the ATK-Forcefield as well, there is no literature present for calculating the minimum displacement.
What should be done in order to create an interface?
Any comments would be appreciated.C

8

General Questions and Answers / TiO2 nanotube

« on: September 19, 2017, 22:50 »

Hello Sir,
How can we form a nanotube of TiO2(titania)?
In a tutorial video for a tube of MoS2, they have considered 2,1,0 values for A' in super cell for converting the lattice to orthorhombic. I tried it for the TiO2 but the resultant structure is not satisfactory.

9

General Questions and Answers / TiO2-CQD-TiO2 junction

« on: September 11, 2017, 11:41 »

Dear ATK users,
How to form a nano-composite of TiO2 and carbon quantum dot, where TiO2 are the left and right electrodes, for simulating its one dimensional conductance.