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.


Topics - qweasel

Pages: [1]
1
General Questions and Answers / How to suppress intermediate output of CrystalStructurePrediction?
« on: April 30, 2017, 20:19 »
I'm using CrystalStructurePrediction inside a script. How can I suppress the intermediate output of this function? I'm not interested for the detailed progress to be printed on the screen. Also, I couldn't find documentation for that function and its output data structures.

2
General Questions and Answers / Why I don't see LSDA under "Exchange correlation"?
« on: February 21, 2017, 02:38 »
I'm following your paper in PRB, where you used LSDA for Ni-graphene interface.

According to the NiO tutorial, LSDA is supposed to be listed under "Exchange correlation". However I only have LDA, GGA and MGGA there.

3
General Questions and Answers / How to build non-covalent graphene-metal interface?
« on: February 21, 2017, 01:48 »
In the tutorial "Graphene–Nickel interface", Ni is covalently bonded to graphene. In reality, it does not necessarily happen. What would be the correct way to attach/couple a non-covalent electrode to graphene?

4
General Questions and Answers / MoS2 nanotube tutorial refers to dftb.org, but no MoS2 sets are available there
« on: February 17, 2017, 04:21 »
The MoS2 nanotube tutorial refers to [STT+00] and to dftb.org downloads, but no MoS2 parameter sets are availble.

What do I do?

5
General Questions and Answers / What is the meaning of "current" in IV curves of periodic structures?
« on: February 17, 2017, 03:13 »
What is the meaning of current in periodic structures that are infinite in A and B directions?
Why is it "current" and not "current density"?

6
General Questions and Answers / Geometry for transmission spectrum calculations: bulk or device?
« on: February 16, 2017, 17:56 »
In this tutorial a bulk configuration with the smallest unit cell is used for transmission spectrum, while in this tutorial a device configuration is used for transmission spectrum as well as other transport calculations. It also states:

Quote
electron transport calculation requires open boundary conditions in the transport direction

Is it correct to use bulk configuration to calculate transmission spectrum for more complex geometries?

7
General Questions and Answers / Which electrons are plotted in electron density plots?
« on: February 15, 2017, 01:50 »
When plotting results of "ElectronDensity" calculation, which electrons contribute to the calculated density?

8
General Questions and Answers / Why default k_A, k_B, k_C values vary for bulk and for device?
« on: February 14, 2017, 01:03 »
When a simple bulk structure is sent to the script generator, the default values for k-point sampling density are kA=kB=kC=2, while for a device the default values are kA=kB=2, kC=400. Why the difference?

9
General Questions and Answers / Poisson solver settings for Electronic Transport Through A Distorted Nanoribbon
« on: February 13, 2017, 23:54 »
In the video "Electronic Transport Through A Distorted Nanoribbon", the settings of the Poisson solver are kept as default (FFT, periodic boundary conditions).

Why is that? If it's a ribbon, wouldn't more suitable boundary conditions be non-periodic?

10
General Questions and Answers / How to add multiple cut planes in the Viewer?
« on: February 10, 2017, 15:02 »
I would like to visualize calculation results (e.g. electron density) using 2 perpendicular cut planes. When I open the viewer I'm asked either isosurface or cut cut plane. Afterwards, under "Properties"->"Cut planes" I don't see any option to add a second cut plane. How can I achieve this?

11
General Questions and Answers / What is the correct way to build an armchair-zigzag heterostructure device?
« on: February 9, 2017, 15:24 »
From first look, dragging a zigzag into an armchair and using move->fuse and quick optimizer seems to work. However, when I do hydrogen passivation, several artefacts become apparent (see attach):
  • Only part of the edges got passivated.
  • Several "normal" sp2 hybridized carbons were unnecessarily passivated.
What is the correct way to make such a device?

12
General Questions and Answers / Job Manager feature request: add properties for job start/finish/total times
« on: February 9, 2017, 14:23 »
To figure out how long a job ran I have to dive into multiple log files and extract the total runtime manually. Could you add a start/finish/total time properties for each job?

13
General Questions and Answers / Why density of states of graphene ribbon with PBC depends on ribbon dimensions?
« on: February 9, 2017, 04:27 »
I used VNL to calculate DoS of graphene for two cases:
(1) One unit cell, with periodic boundary conditions,
(2) 4x4 ribbon (case (1) repeated 4 times in 2 directions), with periodic boundary conditions.

The resulting DoS charts are very similar qualitatively, the major difference being a 20x higher DoS for the ribbon case.
Why is this the case if I'm using PBC? Why the DoS changes with the size of the unit cell?

14
General Questions and Answers / Why k-point density is given in angstroms?
« on: February 8, 2017, 17:34 »
The unit for "Density" of k-point sampling in density of states calculation is given in angstroms (default value=2).
  • What does it mean? Is it N*a/2pi? Why not just unitless N?
  • So larger value means higher k resolution (dk=2pi/Na)?

15
General Questions and Answers / How to manipulate MoS2 single layer into a rectangular device structure?
« on: January 27, 2017, 01:07 »
Building an MoS2 device is not the same as graphene device because:
  • The unit cell is not conventional, and converting it to conventional is not possible (the Super lattice -> Conventional button is gray).
  • When MoS2 is imported from the database, the C axis is perpendicular to the sheet plane. So I cannot make device from bulk.
  • If I rotate it (Coord -> Rotate) 90deg around y, then 60deg around x, the sheet gets messed up (see attach).
  • If I enlarge the cell prior to rotation the sheet is not messed up. However, Neuman condition for the Poisson solver is not available: I can only choose between periodic and dirichlet (and A, B direction are not really front-back, bottom-top).
So what is the correct way of making a rectangular MoS2 device?

Pages: [1]