Phonon Dispersion

[Dipankar Saha]

Can anybody help me to find out the phonon dispersion, for any 2D material (e.g., graphene), using vnl 13.8.b1

[kstokbro]

Add a calculator (use ATK classical for speed)
Add a phonon bandstructure object
perform the calculation
done

[Anders Blom]

When you have a DeviceConfiguration in the Scripter, only the Analysis options that are relevant for devices are shown. You can only compute the phonon band structure for a BulkConfiguration, just like you need a bulk structure to calculate the electron band structure.

[Anders Blom]

It's not so much the point what the device is made of etc. It's the same question as for the electronic band structure, as I wrote above. If you want to calculate a quantity which is a property of a bulk system (like band structure or phonon dispersion) you must use a periodic system, and a device is not periodic (in Z). So if you want to know the phonon dispersion of a 4-AGNR system, then make a 4-AGNR unit cell as a BulkConfiguration and compute it. A device structure doesn't have the property phonon dispersion, just as it doesn't have a band structure.

[Dipankar Saha]

Hi all ...  / Can anybody suggest the way out (regarding the problem as described below)...
____________________
Structure: Armchair GNR
Width: 4
C direction repetition: 10
Passivated with: H+
Now, while trying to find out the Phonon Band Structure, with ATK-extended Huckel(K points 1,16,16; Grid Mesh cutoff 10 Hartree), the problem is... It's is not getting converged in the end. Now if  I choose ATK Classical(E0,E1-- 0 eV, 4eV)....then I'm getting the result, but that is not satisfactory at all (Simply  a few straight lines between the G, Z points)

[Nordland]

Never use Huckel for anything with forces except if you have your own pair-potential at hand.

If I follow the recipe given above, this is my results:

[Dipankar Saha]

Thank u Norland... for all those details.../ Bt, again, there will be the question, that how can I use the calculator (as mentioned in your code), called "TersoffCalculator"
_______________________

Error showing in Log:


# ------------------------------------------------------------ #
+------------------------------------------------------------------------------+
|                                                                              |
| Atomistix ToolKit 13.8.b1 [Build a1c2415]                                    |
|                                                                              |
+------------------------------------------------------------------------------+
Traceback (most recent call last):
  File "c:\users\user\appdata\local\temp\0223720281437294.py", line 368, in <module>
    calculator = TersoffCalculator(parameters=Tersoff_CH_2005())
NameError: name 'Tersoff_CH_2005' is not defined
+------------------------------------------------------------------------------+
| NanoLanguageScript execution finished                                        |
+------------------------------------------------------------------------------+
 

[Nordland]

Sorry my bad.

I will upload a new version of the script.

[Nordland]

Alternative you can also change the calculator to the Brenner calculator

Code

calculator = BrennerCalculator()

[Dipankar Saha]

Sir
while running the Phonon Transmission Spectrum....for a simple two electrode Graphene Device.... I am getting the folllowing error.....
May I know, where is it going wrong??
_____________________________

Traceback (most recent call last):
  File "/tmp/9951790614159924.py", line 396, in <module>
    self_energy_calculator=KrylovSelfEnergy(),
  File "./zipdir/NL/Analysis/PhononTransmissionSpectrum.py", line 108, in __init__
  File "./zipdir/NL/ComputerScienceUtilities/Timer.py", line 45, in __call__
  File "./zipdir/NL/Analysis/PhononTransmissionSpectrum.py", line 107, in <lambda>
  File "./zipdir/NL/Analysis/PhononTransmissionSpectrum.py", line 333, in calculatePhononTransmissionSpectrum
  File "./zipdir/NL/Analysis/PhononTransmissionSpectrum.py", line 359, in calculateDevicePhononTransmissionSpectrum
  File "./zipdir/NL/Calculators/DeviceCalculatorInterface.py", line 145, in _dynamicalMatrix
  File "./zipdir/NL/Calculators/DeviceCalculatorInterface.py", line 398, in downgrade
  File "./zipdir/NL/Calculators/SlaterKosterCalculator/Builders/DeviceSlaterKosterBuilder.py", line 351, in downgrade
NL.ComputerScienceUtilities.Exceptions.NLError: Internal Error - Trying to use non EquivalentBulk density.

[Anders Blom]

It's an odd error message, but my suspicion is that your Slater-Koster method doesn't have a pair potential and hence cannot be used to compute phonon properties (or perform geometry optimization, etc).

[Dipankar Saha]

That may be...let me check..../ Thanks... /
In this regard, let me ask you something.....   Considering the calculation time, complexity and obviously the accuracy....can you please suggest that, which calculator will be a better option to choose while calculating the Phonon Transmission Spectrum of any simple device structure (say, for example 8-AGNR with 12 repetitions in c direction)??

[Anders Blom]

Classical potentials is more or less the only sensible option unless you have a very powerful cluster to parallelize on. The results should be ok - but of course one needs to be aware of the limitations of an empirical method.

[Dipankar Saha]

Yes, that's true.../  thanks.....