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Messages - Petr Khomyakov

Pages: [1] 2 3 ... 74
2
Questions and Answers / Re: different Transmission
« on: November 14, 2019, 23:51 »
I do not know if they are actually different or not, but what one may see comparing these 2 plots, that transmission spectrum is plotted on log/linear scale on the left-hand/right-hand plot, i.e., transmission profiles look different, but the actual numbers should be the same.

3
You can impose periodic boundary condition on each of the 6th facets of your simulation box by treating your system as Bulk Configuration, which is assumed by default in the Builder. Boundary conditions for each facet can also be set in the Scripter or actual script when setting up the Poisson solver, see https://docs.quantumatk.com/manual/includes/PoissonSolvers.html.

5
It really depends on what these statements refer to. If it refers to a single SCF calculation, than one should set tolerance to 10 meV, and that would refer to dE in the log file. In this case, however, this would be pretty poorly-converged total energy in a single SCF calculation.

If 10 meV refers to total energy converges with respect to plane-wave basis set, then it does not refer to dE, but rather to the total energy difference for the PW basis set with the cutoff of 500 eV and the PW basis set with much higher cutoff for which one may say the total energy is converged much better than 10 meV - ideally, one should refer to a complete basis set with infinite cutoff, but this kind of calculation is not possible numerically.   

I do not understand the meaning of the second statement, as 104 eV is ridiculously large number, but if it is set to something small, as given with the tolerance parameter in QuantumATK, then it would refer to dE in a single SCF calculation.

6
Questions and Answers / Re: Optical transition matrix element
« on: November 12, 2019, 09:49 »
To the best of knowledge, the answer is no, also for 3D materials.

7
One should set a restart configuration in a different way for the IVCharacteristics study object, see setCalculator(gate_source_voltage, drain_source_voltage, calculator, initial_state=None) in the manual https://docs.quantumatk.com/manual/Types/IVCharacteristics/IVCharacteristics.html, as well as your modified script attached.

I would also recommend to avoid using filename names with spaces. The latter can always be replaced with underscore "_" or dash "-", for instance.

8
If you are looking for a computationally-cheap approach, you may try using the DFT-LCAO approach with FHI pseudopotentials in compibation with the SZP or DZP basis set.

9
Questions and Answers / Re: Creating a supercell from unit cell
« on: November 11, 2019, 09:14 »
Can I optimize a unit cell and then use the same as a supercell? Would it be  a valid approach.
That is a common approach to optimize a pristine system using a minimal cell. If your supercell derived from this optimized  unit cell is interfaced to something or there are adsorbents on the MoS2 surface, then you may definitely want to do additional geometry optimization of the entire or part of the supercell structure, as suggested in a previous post..

10
Please describe in a step-by-step manner what you did to get this error message. Also, attach your python scripts and related log files.

11
Questions and Answers / Re: k-point units in bandstructure data
« on: November 7, 2019, 14:42 »
Fractional coordinates do not have units by definition, as you may also see when viewing a band structure object in Text Representation. The K-point fractional coordinates are given in the coordinate system of three reciprocal lattice vectors, in terms of fractions of those vectors. 

The Cartesian coordinates are in units of 1/Angstrom,  as can be seen in  Text Representation of the band structure object.

12
Try to increase Fuzz factor in Graphical properties.

13
Please enclose the error message.

14
Questions and Answers / Re: Tolerance Value
« on: November 5, 2019, 09:28 »
Please clarify what you mean by "tolerance of the pictures".

15
I am not sure I understand your issue. One can set a range of V_ds voltages and the number of V_ds voltages such that it will correspond to step dV_ds = 0.02 V. 

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