Topics

1

General Questions and Answers / effective potential

« on: August 22, 2017, 16:44 »

in http://quantumwise.com/forum/index.php?topic=5114.msg22147#msg22147
It tells me I can use effective potential to calculate the electron affinity but the data is really large than I thought. I use the MoS2 supercell and make the vacuum level really large.

2

General Questions and Answers / electronstaticdifferentpotential

« on: August 17, 2017, 23:00 »

I have done the electronstaticdifferncepotential  in ATK which is below. So why does the curve go upward in the FeCl2 region which can be difficult for me to see how the conduction band edge aligns.

3

General Questions and Answers / transmission gap

« on: August 15, 2017, 21:13 »

in this tutorial   http://quantumwise.com/support/tutorials/item/505-transmission-spectrum-of-perfect-sheets-of-graphene-and-mos2
The transmission gap is due to the band gap of MoS2.I am confused why the band structure of the unit cell(hexagonal) can explain it instead of the band structure of the supercell, it says because of the zone  folding effect, I don't understand what that is.

4

General Questions and Answers / how to write a loop in ATK?

« on: July 20, 2017, 21:45 »

I am not familiar with the Python language in ATK, so I want to know how to write a loop in ATK, like if I want to change the vacuum level to change the work function of a material, every time what I do is just stretch the lattice little by little and get the result, it is really time-consuming,  so is there some tutorials to show how to write a code to solve this?

5

General Questions and Answers / effective potential

« on: July 19, 2017, 22:25 »

The effective potential means everything in the Hamiltonian except the kinetic energy(is that right?) So how can I get the work function when I get the effective potential (like  below the effective potential of super cell of MoS2)

6

General Questions and Answers / device bandstructure

« on: June 14, 2017, 20:51 »

The professor asks me to plot the band structure of the device (Fecl2-MoS2-FeCl2) and asks me to make the vacuum level uniform.I am a little bit confused that what does 'making the vacuum level uniform' mean.Does it mean that I have to adjust the vacuum of the FeCl2 region and MoS2 region because of the different work function? If so, how can I do that? I have also done the effective potential calculation. Does it help?  The configuration of the device and the effective potential are posted below.

7

General Questions and Answers / analysis add on error

« on: June 13, 2017, 23:12 »

When I try to plot the bandstructure, the bug comes out.I also attached the Py file.

8

General Questions and Answers / tutorial of work function

« on: June 9, 2017, 17:20 »

Is there any tutorial about how Ec and Ev align with the vacuum level, like work function or affinity?

9

Scripts, Tutorials and Applications / overcome bandgap block

« on: June 2, 2017, 17:53 »

in the FeCl2-MoS2-FeCl2 device, the transmission at the fermi level of both parallel and anti-parallel spin situation is pretty small due to the band gap region blocking the carrier, so how can I  solve this problem，should I add bias on the electrode or something else.

10

General Questions and Answers / TMR calculation

« on: May 26, 2017, 21:40 »

# Calculate conductance for parallel spin
transmission_para = nlread('mgo_para.nc', TransmissionSpectrum)[0]
conductance_para_uu = transmission_para.conductance(spin=Spin.Up)
conductance_para_dd = transmission_para.conductance(spin=Spin.Down)
conductance_para = conductance_para_uu + conductance_para_dd

# Calculate conductance for anti-parallel spin
transmission_anti = nlread('mgo_anti.nc', TransmissionSpectrum)[0]
conductance_anti_uu = transmission_anti.conductance(spin=Spin.Up)
conductance_anti_dd = transmission_anti.conductance(spin=Spin.Down)
conductance_anti = conductance_anti_uu + conductance_anti_dd

print 'Conductance Parallel Spin (Siemens)'
print 'Up=%8.2e, Down=%8.2e' % (conductance_para_uu.inUnitsOf(Siemens),
                                conductance_para_dd.inUnitsOf(Siemens))
print 'Total = %8.2e' % (conductance_para.inUnitsOf(Siemens))
print

print 'Conductance Anti-Parallel Spin (Siemens)'
print 'Up=%8.2e, Down=%8.2e' % (conductance_anti_uu.inUnitsOf(Siemens),
                                conductance_anti_dd.inUnitsOf(Siemens))
print 'Total = %8.2e' % (conductance_anti.inUnitsOf(Siemens))
print

print 'TMR (optimistic)  = %8.2f percent' % \
      (100.*(conductance_para-conductance_anti)/conductance_anti)
print 'TMR (pessimistic) = %8.2f percent' % \
      (100.*(conductance_para-conductance_anti)/(conductance_para+conductance_anti))
In the MTJ tutorial the TMR can be calculated by this code, so what does[0] mean? does it mean the TMR of zero energy?

11

General Questions and Answers / job manager error

« on: May 12, 2017, 22:00 »

My lab ATK version is 13.8.1 and when I try to do some calculation, the job fails and the log shows 'Value error:invalid \x escape. Every calculation can not be used(bandstrcuture,total energy...).