Question: I am getting RuntimeError in one of my calculations using VASP. How can I resolve this?
RuntimeError: *** error - computed ncnt=18134 != input nplane=18133
Answer: VASP does not write which plane waves it uses to the WAVECAR file. Therefore, when banduppy (specifically IrRep) reads the band structure, it tries to mimic VASP's selection and ordering of plane waves that fall within the cut-off sphere. Occasionally, due to numerical errors, one code might consider a plane wave within the sphere while the other does not. This discrepancy can result in an extra vector, as seen in the above case. To address this, use a small correction coefficient (_correct_Ecut0) value. This slightly adjusts the Ecut to either exclude or include plane waves near the boundary of the cut-off sphere. In the example case, use small negative correction to exclude plane waves near the boundary of the cut-off sphere. Use small positive correction when computed ncnt < input nplane.
bands = banduppy.BandStructure(code="vasp", spinor=spinorbit, fPOS = "POSCAR", fWAV = "WAVECAR", _correct_Ecut0=-1e-7)
Question: BandUP code needed both the primitive unit cell and supercell POSCAR files. But in Banduppy it seems only POSCAR_SC is needed. What do I need to modify if I want to do calculations with a different primitiveunit cell and where does it come?
Answer: In a broader sense, for unfolding, we need to know the relationship between the supercell and the reference primitive unit cells on which we want to project your supercell eigenstates. Mathematically, they are related by a matrix transformation: A = M.a. Here, the primitive cell lattice vectors (a_i) (i = 1, 2, 3) form the building unit for the supercell vectors ( A_i), and the two sets of basis vectors are related by the transformation matrix M.
Now, we can provide the primitive unit cell POSCAR (for a) and supercell POSCAR (for A), and software internally calculates the relation between them (M). => BandUP Alternatively, we can provide the supercell POSCAR (A) and the transformation matrix (M) as inputs, and software internally calculates the reference primitive cell (a). => BandUPpy
The information required is essentially the same for BandUP and BandUPpy, only alternative ways.
Regarding the necessary modifications for different reference primitive unit cell calculations: you need to adjust the super_cell_size parameter in for example the run_banduppy_vasp.py, which is the primitive-to-supercell transformation matrix.
Question: How can I write the label Gamma (Greek letter) instead of G in the plots?
Answer: You have to use the list.
special_k_points = ["L","G","X","U","K",r'$\Gamma$'] #instead of "LGXUKG"
Question: How one can remove the text with 'supercell and unfolded' that is displayed over the bands in the figure?
Answer: To turn off the legends, you can use 'show_legend=False' in banduppy.Plotting.plot_ebs() function.
Question: How can change the color of the gray supercell points to a different color or lighter shade?
Answer: Unfortunately, at the moment, the supercell points color can not be changed from banduppy.Plotting.plot_ebs().
If you are not satisfied with the answers, cannot find an answer to your question, or have new suggestions, please feel free to reach out to us. We are committed to providing the best experience for our users and greatly value your feedback.
Have fun with BandUPpy!
Best wishes,
The BandUPpy Team