[vasp] run DMFT on the irreducible BZ with symmetrization

[the-hampel]

Add an IBZ mode to the VASP converter so DMFT can run on the irreducible Brillouin zone (with space-group symmetrization) instead of unfolding to the full k-grid. On a dense NiO mesh this is ~10x fewer k-points and ~9x faster Gloc for an identical result.

New module triqs_dftkit.vasp.symmetry:

• real cubic-harmonic rotation matrices D^l(R) for l=1,2 (tensor method, basis orders matching VASP: d=[xy,yz,z2,xz,x2-y2], p=[y,z,x])
• read VASP symmetry from vaspout.h5; convert the reciprocal-fractional symops to Cartesian and close them into the full point group (VASP only stores one coset representative per k-point, which is incomplete on coarse/special meshes)
• atom permutations under the space group (with translation detection)
• build the dft_symmcorr_input payload (mat/perm/time_inv) consumed by triqs_modest / dft_tools to restore the full-BZ average

converter.convert_dft_input gains use_ibz (auto-detect from vaspout.h5), vasp_h5 and plo_cfg arguments: in IBZ mode it slices the data to the irreducible k-points, sets bz_weights to the IBZ multiplicities and symm_op=1, and writes the real symmetry matrices. Without symmetry data (text mode) it falls back to the full grid and suggests the h5 interface.

Tests: converter IBZ tests for SrVO3 (t2g, cubic) and AFM NiO (full d + O p, non-cubic, two equivalent Ni); ignore generated test artifacts.

[harrisonlabollita]

Hi @the-hampel, now that we have the IBZ symmetry operations are they in the same format as the Wien2k IBZ symmetry ops? Then the DFTtools and ModEST symmetrizers can consume the same data and apply the symmetrization to k-summed quantities.

[the-hampel]

Hi @harrisonlabollita ,
yes i think wien2k and VASP work similar here. For example for this to work I did not have to change anything in triqs/dft_tools . In modest I have a branch: https://github.com/TRIQS/modest/tree/vasp_ibz that just adds a test to modest (+ an important bug fix in the p-orbital oder modest assumes for VASP!) . Is this answering your question? I must admit I let Claude code the symm ops of the orbitals (I was too lazy for this since years - otherwise this would have not taken so long ^^) . I designed the tests where I knew it would only pass if the symm ops are correct, so I hope the implementation is along the same lines as Wien2k. I just fixed some minor things here for non complete projector sets. Happy also discuss this next week. This has lower prio than the other PRs for me - or is more experimental.

[harrisonlabollita]

That answers my question! Thank you

[the-hampel]

Note after seeing all these comments on Wien2k with SOC: I did not think or test this with SOC. I am not sure if I have to be careful with anything in that case. TBD next week as well.