Line mode and reciprocal density bug int MPHSEBSSet

[fraricci]

Python version

python 3.11

Pymatgen version

2024.1.27

Operating system version

No response

Current behavior

In: mpset = MPHSEBSSet(st, mode="Line",reciprocal_density=100)
Out: Correct list of kpoints

In: mpset = MPHSEBSSet(st, mode="Line",user_kpoints_settings={"reciprocal_density":100})
Out:

pymatgen with grid density = 1239 / number of atoms
0
Gamma
2 2 2

Expected Behavior

In: mpset = MPHSEBSSet(st, mode="Line",user_kpoints_settings={"reciprocal_density":100})
Out: Correct list of kpoints

Minimal example

No response

Relevant files to reproduce this bug

No response

[utf]

Hi @fraricci, thanks for bringing this up.

In the older version of MPHSEBSSet, setting user_kpoints_settings={"reciprocal_density":100} wouldn't have any effect. It was simply ignored.

In the new version of the input sets, the user_kpoints_settings is strictly respected. In this case you are only asking for uniform k-points, hence no line mode k-points none are generated. If you want to produce line mode k-points you'd have to do:

mpset = MPHSEBSSet(
    st, 
    mode="Line",
    user_kpoints_settings={"reciprocal_density":100, "zero_weighted_line_density": 20}
)

The reason for this is that I wanted to always respect user_*_settings. If for some reason you want to use the rest of the HSE line mode settings but with a uniform mesh, then this should be possible. This is in contrast to the older input sets where user_kpoints_settings was completely ignored in MPHSEBSSet.

The recommendation is to simply configure everything using the init parameters, which will configure the k-points for you. For completeness, these are:

MPHSEBSSet(
    reciprocal_density=50,                # controls density of weighted uniform mesh for all modes
    kpoints_line_density=20,              # controls density of zero weighted line k-points for mode=line
    zero_weighted_reciprocal_density=100  # controls density of zero weighted uniform for mode=uniform_dense
)

[fraricci]

Hi @utf , thanks for the explanation here.

Though, I still find this behavior a little obscure for these reasons:

1. If I want to use the user_kpoints_setting I need to set all the keys and not just the one I want to change. Shouldn't just take the rest from the init params?
2. Apparently, when only a single key is set, reciprocal_density in this case, the mode is changed internally and not transparently.
3. The key zero_weighted_line_density spells differently from the init param kpoints_line_density but they represent the same thing. Shouldn't be called the same? This is something I found also in other sets...

Anyway, I agree the best way is to just use the init parameters.