Combine the GPAW and VASP ab initio potential tutorials into one page

[TomaSusi]

Combines the VASP documentation contributed by a tester with the existing GPAW tutorial, and renames the page from ab initio potentials with GPAW to ab initio potentials.

The page now covers all three routes to a DFT potential in one place:

	takes	core electrons from
GPAWPotential	a converged GPAW calculator	the GPAW setups
VASPPotential	AECCAR2 + POTCAR	the POTCAR radial core density
ChargeDensityPotential	any valence density as a NumPy array	an analytic Slater model

Structure

• ab initio potentials — intro, pointing at the three routes
• Potentials from a GPAW calculation — the existing hBN walkthrough, unchanged
• Potentials from a VASP calculation — the contributed SrTiO₃ walkthrough: setting up the VASP run, loading the files, building and comparing the four potentials, diffraction, a thickness series
• How accurate are the core models? — the contributor's validation table across SrTiO₃, hBN and MoS₂
• Further reading

What changed in the GPAW half

Nothing, apart from the headings being demoted one level under the new section — 21 of its 28 cells are byte-identical — and one fix. The citation of the experimental intensities was written ​`cite`{gpawpotential}, with the braces and backticks the wrong way round and the key missing its final s, so it rendered as literal text instead of a citation. It now resolves.

What changed in the contributed half

The code is as the contributor wrote it. The edits are editorial:

• headings demoted to sit under the VASP section
• references to "the chapter ab initio potentials with GPAW" rewritten, since it is now a section of the same page
• abTEM spelled *ab*TEM, as elsewhere in the docs
• the four wide figures tagged full-width
• a dead material_name assignment dropped
• the import cell reduced to the VASP-specific imports and left visible, since numpy/matplotlib/abtem are already imported in the hidden setup cell at the top

Notes

• The file name stays charge_density.ipynb, so the published URL and the (walkthrough:charge_density) label referenced from the potentials walkthrough keep working. Only the title changes.
• Notebooks are not executed at build time (execute_notebooks: 'off'). That is what makes the VASP half possible: POTCAR files are under the VASP license, so nothing executable can be shipped. Its cells carry the contributor's stored outputs and read from path/to/... placeholders, which the text says explicitly.
• jupyter-book build docs/ is clean for this page — no new warnings, and the three new cross-references resolve.
• VASPPotential and ChargeDensityPotential(valence_electrons=...) are not released yet; they are in abTEM#395 and abTEM#422. This page should land after those.
• The VASP material is someone else's work — you may want to add them as a co-author on the commit, or credit them on the page, before merging. I did not guess at a name or address.

🤖 Posted by Claude Code on behalf of Toma