Messages

436

General Questions and Answers / Re: difference between I-V curves for periodic and nonperiodic central region

« on: March 28, 2014, 10:25 »

looks like you already answered yourself!

the first configuration is a graphene sheet (2D periodic) and the second is a nanoribbon (1D periodic). Very different structures.

Indeed, you can have a device which is also periodic in the x and y directions.

437

General Questions and Answers / Re: Multiferroic tunnel junctions

« on: March 26, 2014, 09:33 »

Hello,

To set FE state i try to displace atoms and set small bias but geometry optimization gave me constantly different wrong results.

can you please clarify what do you mean here with "wrong results"? zero displacement?
Also how do you displace the atoms and add the small bias? (entire script maybe?)

to answer to your last question, how to setup ferroelectronic state, you can apply a small voltage and optimize as suggested in the old discussion.
In ATK you can optimize the geometry under an applied voltage. It can be a time consuming calculation though.

438

General Questions and Answers / Re: Strain after optimization

« on: March 24, 2014, 09:37 »

The matrix printed is the stress tensor, each element represents the stress acting in a particular face in a particular direction.

As zh suggested, check also the manual http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.stress.html

439

Installation and License Questions / Re: Installation and Running Issues in Ubuntu

« on: March 24, 2014, 09:32 »

That is another FAQ:
http://quantumwise.com/support/faq/116-libglso-cannot-open-shared-object-file?catid=25%3Ainstallation-issues

try if it works.

440

Gallery / Pillared Graphene

« on: March 19, 2014, 22:48 »

take a CNT and a graphene sheet and mix them together in the Builder!

for a reference see for example G. Dimitrakakis et al. Nano Lett., Vol. 8, No. 10, 2008

In different flavours!

441

General Questions and Answers / Re: Extract analysis data from .nc file

« on: March 19, 2014, 10:19 »

1. How can I export the I-V data for Symmetrize?

By exporting/plotting -IV.biases() and -IV.currents()

2. How can I export the current values in the unit of nA? (current is exported in A)

something like:
currents = IV.currents().inUnitsOf(Ampere)*10**9

3. The energy is set to the Average Fermi level or Absolute energy in the Exported DOS data using these python script?

It depends on the energy_zero_parameter you set in the input script.
http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.densityofstates.html

442

General Questions and Answers / Re: Extract analysis data from .nc file

« on: March 18, 2014, 10:32 »

did you include
IV = nlread('analysis.nc',IVCurve)[0] ?

443

General Questions and Answers / Re: Extract analysis data from .nc file

« on: March 18, 2014, 10:25 »

try:

Code

IV = nlread('analysis.nc',IVCurve)[0]
print IV.biases(), IV.currents()

444

News and Announcements / New Tutorial: Computing the Young's modulus of a CNT with a SW defect with MD

« on: March 17, 2014, 11:19 »

New tutorial uploaded!
Here: Computing the Young's modulus of a carbon nanotube with a Stone-Wales defect using molecular dynamics

445

General Questions and Answers / Re: Minimizing molecules on Si(100)

« on: March 17, 2014, 10:13 »

you can have more accurate results by increasing the mesh cut-off, changing the basis set...

or, maybe your calculation is more accurate!

446

General Questions and Answers / Re: Extract analysis data from .nc file

« on: March 17, 2014, 09:50 »

yes, of course it is possible.
In most of the tutorials we do that
random example: http://quantumwise.com/publications/tutorials/mini-tutorials/235#h6-analyzing-the-results

check also the single manual pages under "usage examples" to find useful examples.

in general you read the data with something like:
dos = nlread('dos.nc', DensityOfStates)

Finally, also note that you can export data in a text file directly from the LabFloor

447

General Questions and Answers / Re: Atom Adsorption on Electrode -reg

« on: March 4, 2014, 20:54 »

It refers to the surface adsorption sites for your atom or molecule.

448

General Questions and Answers / Re: No of atoms and simulation-reg

« on: March 4, 2014, 20:33 »

all the tutorials are listed in the Tutorials section of the website:
http://quantumwise.com/publications/tutorials
mini-, longer, builder tutorials, ecc ecc.. all you may need.
A useful link is also the Manuals page: http://quantumwise.com/manuals


You are looking for the "Estimating the memory usage for a calculation" mini-tutorial.

449

General Questions and Answers / Re: Gold Electrode-reg

« on: March 3, 2014, 08:22 »

The Au(111) surface is more stable than the (100) or the (110) surface (lower surface energy), which is true for most of the fcc metals.

However, depending on the experimental conditions or on how the surface is cleaved and so on, you can expect the (100) or the (110) surface, vicinal surfaces, reconstructed surfaces, ...
You can find references about Au(100) electrodes for example.

Of course in VNL you can chose the hkl indices by using the surface cleave plugin in the Builder and build whatever electrode you wish!

450

General Questions and Answers / Re: Geometry Optimization

« on: February 28, 2014, 15:42 »

There is nothing wrong with your calculations, the job finished because it reached all the convergence criteria you set.
In particular the maximum stress criteria of 0.01 eV/Å**3.
You can check it if you include the Stress analysis in the calculation:

Code

+------------------------------------------------------------------------------+
| Stress Report                                                                |
+------------------------------------------------------------------------------+
| [[  9.05881942e-03   5.25907270e-31   7.88860905e-31]                        |
|  [  7.89246091e-31   9.05881942e-03   5.25907270e-31]                        |
|  [  5.26356654e-31   6.57319890e-31   9.05881942e-03]] eV/Ang**3             |
+------------------------------------------------------------------------------+

You should use a much lower value, something like 0.001 eV/Å**3.
See for example here this section: http://quantumwise.com/publications/tutorials/mini-tutorials/244#h3-setting-up-the-bulk-configurations