Questions for mp-28256, V2Se9


#1
  1. Structure files (CIF, VASP, POSCAR, etc) contains V8Se36, and two lattice angles are 90 degree. However, Lattice Parameters shows that alpha = 101.477, beta = gamma = 96.141 degree. And final structure section in the web page shows only V4Se18.
    If I calculate the band structure of V2Se9 from the structure file by VASP, the band structure contains about twice many band comparing the band structure on the web page. I guessed that the band structure would be calculated from the Final structure section, not structure file.

  2. However, even I calculated the band structure from Final structure, the number of band is similar to that in the web page, but they are not same. I used the parameters in Datailed input parameters and outputs for all calculations. What’s the problem?


#2

Hi, sorry for the delay on this. There are a couple of things to clarify, you can see all of the input parameters for the VASP calculations associated with mp-28256 here. In general, our approach to associating calculations is to aggregate them based on structural equivalence using pymatgen’s StructureMatcher, so there are occasionally cases where certain calculations which don’t necessarily have exactly the same input structure (but are determined to be equivalent within a tolerance) are compiled into a single materials document.

If you inspect the task documents, you can see that the structure representations for the GGA Structure Optimization and the GGA NCSF Line calculations are slightly different, in that the crystal axes have been reoriented such that the angles are all <90, but the structures are the same. I’m not entirely sure how this particularly change occured, because our standard workflow simply copies the output from one calculation to another, but they are valid. If you want to determine an apples-to-apples comparison of our bandstructures, try using the input structure (and the input parameters) listed in the GGA NSCF task.

Also, the lattice parameters are determined from standard representations (e. g. conventional/primitive) of the structure derived the pymatgen and spglib, so the parameters shown in the structure viewer on the materials detail page may be different from those shown in the “final_structure” fields.

We appreciate you bringing this to our attention, as it seems pretty confusing to have so many different representations of the structure. We’ll look into ways we might reduce the inconsistencies, or at least present some of the data with a more unified structure representation.

Let me know if you have further questions.


#3

Thank you for the reply.

Excuse me, but I have more questions.

  1. The GGA NSCF calculations have their KPOINTS file. For example, mp-700860_kpoints.txt from NSCF uniform:

Kpoints from vasprun.xml
1
Reciprocal
0.0 0.0 0.0 0
0.125 0.0 0.0 0
0.25 0.0 0.0 0
0.375 0.0 0.0 0
0.5 0.0 0.0 0
0.125 0.125 0.0 0
0.25 0.125 0.0 0
0.375 0.125 0.0 0
0.5 0.125 0.0 0
-0.375 0.125 0.0 0
-0.25 0.125 0.0 0
-0.125 0.125 0.0 0
0.25 0.25 0.0 0
0.375 0.25 0.0 0
0.5 0.25 0.0 0
-0.375 0.25 0.0 0
-0.25 0.25 0.0 0
0.375 0.375 0.0 0
0.5 0.375 0.0 0
-0.375 0.375 0.0 0
0.5 0.5 0.0 0
0.0 0.0 0.125 0
0.125 0.0 0.125 0
0.25 0.0 0.125 0
0.375 0.0 0.125 0
0.5 0.0 0.125 0
-0.375 0.0 0.125 0
-0.25 0.0 0.125 0
-0.125 0.0 0.125 0
0.125 0.125 0.125 0
0.25 0.125 0.125 0
0.375 0.125 0.125 0
0.5 0.125 0.125 0
-0.375 0.125 0.125 0
-0.25 0.125 0.125 0
-0.125 0.125 0.125 0
0.25 0.25 0.125 0
0.375 0.25 0.125 0
0.5 0.25 0.125 0
-0.375 0.25 0.125 0
-0.25 0.25 0.125 0
-0.125 0.25 0.125 0
0.375 0.375 0.125 0
0.5 0.375 0.125 0
-0.375 0.375 0.125 0
-0.25 0.375 0.125 0
-0.125 0.375 0.125 0
0.5 0.5 0.125 0
-0.375 0.5 0.125 0
-0.25 0.5 0.125 0
-0.125 0.5 0.125 0
-0.375 -0.375 0.125 0
-0.25 -0.375 0.125 0
-0.125 -0.375 0.125 0
-0.25 -0.25 0.125 0
-0.125 -0.25 0.125 0
-0.125 -0.125 0.125 0
0.0 0.0 0.25 0
0.125 0.0 0.25 0
0.25 0.0 0.25 0
0.375 0.0 0.25 0
0.5 0.0 0.25 0
-0.375 0.0 0.25 0
-0.25 0.0 0.25 0
-0.125 0.0 0.25 0
0.125 0.125 0.25 0
0.25 0.125 0.25 0
0.375 0.125 0.25 0
0.5 0.125 0.25 0
-0.375 0.125 0.25 0
-0.25 0.125 0.25 0
-0.125 0.125 0.25 0
0.25 0.25 0.25 0
0.375 0.25 0.25 0
0.5 0.25 0.25 0
-0.375 0.25 0.25 0
-0.25 0.25 0.25 0
-0.125 0.25 0.25 0
0.375 0.375 0.25 0
0.5 0.375 0.25 0
-0.375 0.375 0.25 0
-0.25 0.375 0.25 0
-0.125 0.375 0.25 0
0.5 0.5 0.25 0
-0.375 0.5 0.25 0
-0.25 0.5 0.25 0
-0.125 0.5 0.25 0
-0.375 -0.375 0.25 0
-0.25 -0.375 0.25 0
-0.125 -0.375 0.25 0
-0.25 -0.25 0.25 0
-0.125 -0.25 0.25 0
-0.125 -0.125 0.25 0
0.0 0.0 0.375 0
0.125 0.0 0.375 0
0.25 0.0 0.375 0
0.375 0.0 0.375 0
0.5 0.0 0.375 0
-0.375 0.0 0.375 0
-0.25 0.0 0.375 0
-0.125 0.0 0.375 0
0.125 0.125 0.375 0
0.25 0.125 0.375 0
0.375 0.125 0.375 0
0.5 0.125 0.375 0
-0.375 0.125 0.375 0
-0.25 0.125 0.375 0
-0.125 0.125 0.375 0
0.25 0.25 0.375 0
0.375 0.25 0.375 0
0.5 0.25 0.375 0
-0.375 0.25 0.375 0
-0.25 0.25 0.375 0
-0.125 0.25 0.375 0
0.375 0.375 0.375 0
0.5 0.375 0.375 0
-0.375 0.375 0.375 0
-0.25 0.375 0.375 0
-0.125 0.375 0.375 0
0.5 0.5 0.375 0
-0.375 0.5 0.375 0
-0.25 0.5 0.375 0
-0.125 0.5 0.375 0
-0.375 -0.375 0.375 0
-0.25 -0.375 0.375 0
-0.125 -0.375 0.375 0
-0.25 -0.25 0.375 0
-0.125 -0.25 0.375 0
-0.125 -0.125 0.375 0
0.0 0.0 0.5 0
0.125 0.0 0.5 0
0.25 0.0 0.5 0
0.375 0.0 0.5 0
0.5 0.0 0.5 0
0.125 0.125 0.5 0
0.25 0.125 0.5 0
0.375 0.125 0.5 0
0.5 0.125 0.5 0
-0.375 0.125 0.5 0
-0.25 0.125 0.5 0
-0.125 0.125 0.5 0
0.25 0.25 0.5 0
0.375 0.25 0.5 0
0.5 0.25 0.5 0
-0.375 0.25 0.5 0
-0.25 0.25 0.5 0
0.375 0.375 0.5 0
0.5 0.375 0.5 0
-0.375 0.375 0.5 0
0.5 0.5 0.5 0

However, this KPOINTS file cannot be used for VASP calculation because all weights of kpoints are zero. It makes error during the NSCF uniform calculation. Why is the KPOINTS file this form? What KPOINTS file should be used?

  1. The first few lines of KPOINTS for NSCF line is following:
    Kpoints from vasprun.xml
    1
    Reciprocal
    0.0 0.0 0.0 0
    0.04170201 0.04170201 0.0044029 0
    0.08340402 0.08340402 0.00880579 0

This file has the same problem as above files. And, there are many k points coordinates, but only first point is used because of second line: only 1 point is needed. Then, what does the other points than first have meanings?