GPAW 26.7.0 native hyperfine_parameters, six real H calculations with legacy PW LDA/PBE.
Periodic cubic vacuum approximation, not an exact isolated H wavefunction or precision prediction of the experimental 21 cm line.
Proton g factor=5.586. Raw native tensors in eV need nuclear g factor and division by net magnetic moment; the spin-flipped case tests normalization.
CPU MPI=1, OMP=1. bash setup.sh; sbatch job.slurm; bash verify.sh; bash plot.sh.
Reference contains full own extracted spin densities and tensor decompositions, no PAW datasets or GPW files.
