GPAW26.7.0 legacy LCAO/dzp PBE water, fixed geometry; common0.30A coarse grid spacing. Six actual boundary controls: small/large default, multipole4/9, extra-vacuum128 cubed direct and coarses1. Coarses1 solves a64cubed coarse grid and restores the small fine grid potential. Direct coarses0 must omit poissonsolver_small.
The large default box is a finite-box comparison, not an exact isolated limit; more multipoles do not guarantee monotonic convergence. Complete density and potential arrays are included, no PAW datasets or GPW checkpoints.
CPU MPI1 OMP1. bash setup.sh; sbatch job.slurm; bash verify.sh; bash plot.sh.
