Topics

16

Future Releases / Rotation along one axis

« on: June 16, 2015, 23:00 »

It would be nice if you could rotate structures along a specific axis when you're visualising them. Another software I use has this and I find it useful: if you hold 'x' while right clicking the structure it's only allowed to rotate along the X axis, and so on for 'y' and 'z'.

Maybe more people would find this useful as rotating structures can sometimes get out of hand (at least for me)  and then I have to reset the view and start trying again to find the angle I want. I've found that "decomposing" the rotations by axis makes it much easier. 

17

General Questions and Answers / Transmission of periodic systems

« on: June 16, 2015, 20:12 »

Hi,

I've been reading around and it is quite clear to me that for perfectly periodic systems the transmission at a certain energy & transverse k-point must be an integer. But should the total transmission at a certain energy be an integer always?

In order to investigate this issue I have been trying to calculate the TransmissionSpectrum of bulk copper. I can see with the transmission analyzer that the number of channels at a particular (E,k) is always an integer ("numerical" integers anyway, e.g. 0.999999...) but then the "total" transmission can be non-integer. Is the total transmission a brillouin zone integration of the  values along the transverse directions and can be non-integer?

It isn't clear to me whether this is a physical result or it just means my calculation isn't  converged (my electrode is too small or not enough k-points, etc). I tried calculating this TransmissionSpectrum in both Device & Bulk Configurations. In both cases I'm getting non-integers. The bulk configuration I used was just one conventional cell and the device configuration included 2x conventional cells along the Z direction as electrodes and 3x as the central region. In all cases the size of both transverse directions was just 1 conventional cell.

Thanks in advance

18

General Questions and Answers / Self energy calculator for transmission pathways

« on: June 11, 2015, 17:06 »

Hi,

I've been reading around about self energy calculators and found that in this thread:

http://quantumwise.com/forum/index.php?topic=3178

Dr. Anders Blom mentions that the Direct calculator is mostly included for historical reasons and that Recursion should be the standard reliable calculator. So my question is:

Is there a reason why the default calculator for TransmissionPathways is DirectSelfEnergy()?

For TransmissionSpectrum the default is RecursionSelfEnergy() in agreement with Dr. Blom's post.

Thanks for your help

19

General Questions and Answers / Checkpoint file in restarted calculations

« on: June 5, 2015, 15:31 »

Hi all,

When running a restarted calculation with a script like:

configuration = nlread('original_checkpoint_file.nc')[0]
configuration.setCalculator(configuration.calculator(), initial_state=configuration)
configuration.update(force_restart=True)
nlsave('output.nc', configuration)

How can one specify the checkpoint file to write to? Since there's no explicit specification of the calculator I don't know how to do it. Is there a way using the setCalculator method?

Thanks!