Messages

1

General Questions and Answers / Down spin conductance higher???

« on: February 5, 2013, 18:27 »

Hi

I am working with organic molecules, to calculate conductance with various transition metal doping. I used Vanadium for doping and got conductance values of 3.9e-5 S and ~2.8e-5 S for Up and Down spins respectively, at 0 Volt bias. However, when I changed the dopant to Cobalt, I got conductance values as 1e-5 and 2e-5 S. According to my understanding, most of the codes treat the electron spin with higher density as UP spin, and the other one as Down spin, so I would expect the decreasing conductance values for both cases, when comparing Up spin to down spin. So, my question is how ATK treats electronic spin? Is it sensible that I get more population of down spin than up spin?

Thanks

2

General Questions and Answers / Re: Transmission pathways calculation from Transmission Spectrum?

« on: January 29, 2013, 21:53 »

Thank you very much. I should have noticed it as it should have been similar to the previous script I was using, but I missed it. Thanks a lot, again. I will update you how it goes.

3

General Questions and Answers / Re: Transmission pathways calculation from Transmission Spectrum?

« on: January 29, 2013, 20:18 »

It's giving me the following error:

SyntaxError: invalid syntax
  File "path.py", line 4
biases = <ul style="margin-top: 0; margin-bottom: 0;"><li type="circle"></li></ul>configurations = []

4

General Questions and Answers / Re: Transmission pathways calculation from Transmission Spectrum?

« on: January 29, 2013, 16:30 »

Hi Anders

Thank you very much. I am trying to test it. I will let you know how it goes.

5

General Questions and Answers / Re: Transmission pathways calculation from Transmission Spectrum?

« on: January 24, 2013, 23:20 »

Hi Anders

Below is the script I was trying to use to calculate for the file containing scf data for different biases, where I could change the bias and also have the pathways calcualted for a range of energies. (Similar to the way IV calculation script was written)

Code

scf_filename = "analysis_%g.nc"
analysis_filename = "pathways_0v.nc"
biases = [0]
configurations = [] 
for bias in biases: 
     configurations.append(nlread(scf_filename % bias, DeviceConfiguration)[0])
biases = [float(conf.calculator().electrodeVoltages()[0]-conf.calculator().electrodeVoltages()[1]) for conf in configurations]
configurations = [configurations[j] for j in numpy.argsort(biases)]
for configuration in configurations:
        calculator = configuration.calculator()
        bias = calculator.electrodeVoltages()[0]-calculator.electrodeVoltages()[1]
        if float(bias) == 0. :  
                zero_bias_potential = ElectrostaticDifferencePotential(configuration) 
                break  
for configuration in configurations:  
    calculator = configuration.calculator()
    bias = calculator.electrodeVoltages()[0]-calculator.electrodeVoltages()[1]
    transmission_pathways = TransmissionPathways(
        configuration=configuration,
        energies=numpy.linspace(-2,8,100)*eV,
        kpoints=MonkhorstPackGrid(1,1),
        energy_zero_parameter=AverageFermiLevel,
        infinitesimal=1e-06*eV,
        contributions=Left,
        spin=Spin.Up,
        self_energy_calculator=DirectSelfEnergy(),
    )
nlsave(analysis_filename, transmission_pathways)
nlprint(transmission_pathways)
geometry = nlread('analysis_0_long.nc', DeviceConfiguration, read_state = False)[0]  
nlsave(analysis_filename, geometry)

Could you please see if this approach can be applied?

Thanks

6

General Questions and Answers / Re: Transmission pathways calculation from Transmission Spectrum?

« on: January 22, 2013, 23:25 »

Hi Anders

Thank you very much for the response. I was trying to use the similar script for transmission pathways, but I was reading the scf output file differently. I was using the version given for IV curve calculation, for different biases, and it kept running for long time without writing anything. I thought it should work on giving me pathways for a range of energies in one file (with command, energies=numpy.linspace(-2,4,50)*eV and for configurations at different biases. Is it incorrect way to do that?

Regards
Ashutosh

7

General Questions and Answers / Transmission pathways calculation from Transmission Spectrum?

« on: January 21, 2013, 18:36 »

Hi

I followed the mini tutorial to calculate transmission spectrum and I-V curve for a device (http://www.quantumwise.com/publications/tutorials/mini-tutorials/98-i-v-curve-and-voltage-drop). I was wondering if it is possible to calculate transmission pathways from the calculated transmission spectra. Since my devices are big, i break it into parts for different biases. Also, if I try to calculate transmission spectrum separately from the scf calculation or the calculated transmission spectra, what should the script look like for spin resolved case? Will I have to calculate for individual spin separately?

Thanks