Installing on Arch Linux

How to make MolForma an Arch Linux package and install it with pacman. makepkg builds the package molforma-git from the repository’s packaging/arch/PKGBUILD. The dependencies come from the official repositories (core, extra) automatically, and NWChem for calculations from the AUR.

These steps are for Arch Linux (x86-64) and MolForma 1.0.0. They were checked on 2026-10-28 (see Verified configuration).

MolForma has no package in the official repositories or the AUR (as of 2026-10-28). The PKGBUILD fetches the source of the main branch on GitHub and builds it. As pacman manages the installed package, pacman -R removes it.

Required packages

makepkg -s installs these packages from the official repositories automatically.

Kind	Packages	Used for
Run time	`qt6-base`	The interface (Qt Widgets)
Run time	`openbabel`	Reading and writing structure files, force-field cleanup, 3D structures from SMILES (includes the format plugins and force-field data)
Run time	`rdkit`	Strict stereo perception (R/S, E/Z), residue recognition
Run time	`vtk`	Drawing the 3D view with VTK (OpenGL)
Build time	`git`, `cmake`, `ninja`, `eigen`	Fetching the source and building
Build time	`boost`, `fast_float`, `nlohmann-json`, `openmpi`	What the CMake configurations of RDKit and VTK refer to

Install these yourself as needed.

Kind	Package	Source	Used for
Required	`base-devel`	core	Making packages with `makepkg` (includes GCC)
Calculations	`nwchem`	AUR	Running calculations. Also brings in `openmpi` and `scalapack` (from the AUR) as dependencies
Optional	`qt6-translations`	extra	With the Japanese interface, Japanese for Qt’s standard dialogs such as file selection too (standard buttons such as “Save” and “Cancel” are Japanese even without it)
Optional	`noto-fonts-cjk`	extra	Japanese fonts (if none are installed)

RDKit and VTKThe PKGBUILD builds with RDKit and VTK, and stops the build when CMake cannot use either of them. Drawing with VTK also needs a GPU driver that provides OpenGL 3.2 or later. rdkit also depends on Python and more, but MolForma uses only its C++ libraries.
NWChemBuilding and saving input (“Save as job”) works without NWChem.

1. Prepare

Update the system and install base-devel and git, which making the package uses. For the optional packages, install them as well.

sudo pacman -Syu --needed base-devel git
sudo pacman -S --needed qt6-translations noto-fonts-cjk

2. Install NWChem (AUR)

The AUR’s nwchem depends on scalapack, which is in the AUR too, so install it with a helper that resolves AUR dependencies (yay here). It is built from source and takes a while.

yay -S nwchem

If yay is not installed, build and install it first as a normal user. Review the PKGBUILD shown before you continue.

git clone https://aur.archlinux.org/yay.git
cd yay
less PKGBUILD
makepkg -si

NWChem goes to /usr/bin/nwchem and its basis set library to /usr/share/nwchem/libraries/. The basis set library works as installed, so you need neither ~/.nwchemrc nor NWCHEM_BASIS_LIBRARY. MolForma’s “3 Run settings” defaults (executable nwchem, launch with MPI, MPI launcher mpirun, 2 processes) launch this NWChem as they are.

3. Make and install the package

Fetch the PKGBUILD into a working folder, review it, then run makepkg. Updating uses the working folder too.

mkdir -p ~/.cache/molforma-arch
cd ~/.cache/molforma-arch
curl -LO https://raw.githubusercontent.com/hnakada123/MolForma/main/packaging/arch/PKGBUILD
less PKGBUILD
makepkg -si

makepkg -si does the following in order.

Installs the missing dependencies with pacman (-s). It asks for the administrator password.
Fetches the source of the main branch on GitHub and builds it. A -- MolForma rendering: VTK 9.7.1 (Qt6), with QPainter fallback line along the way means it draws with VTK. If CMake cannot use VTK or RDKit, it stops here with ==> ERROR: CMake cannot use VTK or similar (see Troubleshooting).
Runs the tests. They use neither NWChem nor the network. To skip them, use makepkg -si --nocheck.
Makes the package (molforma-git-1.0.0.r<commit count>.g<commit id>-1-x86_64.pkg.tar.zst) and installs it with pacman (-i).

The build uses all CPU cores. If memory runs short, lower the number of compile jobs run at once, as in CMAKE_BUILD_PARALLEL_LEVEL=2 makepkg -si.

Building for development without making a package is described in the README.

4. Start and check

The package places these files (pacman -Ql molforma-git lists them). pacman’s hooks update the file type and menu information automatically.

Location	Contents
`/usr/bin/molforma`	The executable
`/usr/share/applications/molforma.desktop`	The application menu entry
`/usr/share/icons/hicolor/`	Icons (`scalable` and `256x256`)
`/usr/share/mime/packages/molforma.xml`	The file types of `.molforma.json` (projects) and `.nw` (NWChem input)
`/usr/share/molforma/`	LICENSE, NOTICE, README and the manual’s Markdown (the manual is also built into the executable)

Run molforma in a terminal or choose “MolForma” in the application menu. If it does not appear in the KDE Plasma menu right away, run kbuildsycoca6. The interface language follows the system language (“Language (after restart)” in “Edit → Preferences…” switches it; it takes effect after a restart).

Open “Help → About MolForma” and check that it reads “MolForma 1.0.0”, “Stereochemistry and residue recognition (RDKit): Enabled” and “3D rendering: VTK (OpenGL)”. Where OpenGL is unavailable, it reads “3D rendering: QPainter (CPU)”.
Open “3 Run settings” and check that below the “NWChem executable” and “MPI launcher” fields appear /usr/bin/nwchem and /usr/bin/mpirun, where PATH found them.
Try a calculation on a small molecule. The steps are in recipe 1 Building from atoms and bonds.

Updating and removing

Updating

Fetch the PKGBUILD again, then make the package again. makepkg fetches the latest source of the main branch, makes a package of the new version and installs it.

cd ~/.cache/molforma-arch
curl -LO https://raw.githubusercontent.com/hnakada123/MolForma/main/packaging/arch/PKGBUILD
makepkg -si

As it is not in the AUR, pacman -Syu and yay -Syu do not update MolForma. If pacman -Syu brings new versions of shared libraries such as Qt, Open Babel, RDKit or VTK and MolForma stops starting with molforma: error while loading shared libraries, make it again with makepkg -sif, even if the source has not changed (-f makes the package again even if one was already made).

Removing

sudo pacman -R molforma-git

The application settings (~/.config/MolForma/), autosaves (~/.local/share/MolForma/), calculation jobs (by default ~/MolForma/jobs) and the working folder (~/.cache/molforma-arch) remain; delete them by hand if you no longer need them. pacman -Qdtq lists the dependencies installed for the build that nothing else uses. sudo pacman -Rs nwchem removes NWChem.

Troubleshooting

Symptom	Check and fix
It stops with `==> ERROR: CMake cannot use VTK`	The `VTK development dependency unavailable:` lines before it name what is missing (`FastFloat::fast_float` is `fast_float`, `nlohmann_json::nlohmann_json` is `nlohmann-json`). Install that package and run `makepkg -si` again
It stops with `==> ERROR: CMake cannot use RDKit`	Check that `boost` is installed and run `makepkg -si` again
A test fails and no package is made	Report it with the output of the failed test in the GitHub issues. To make the package without the tests, use `makepkg -si --nocheck`
Memory runs short during the build	Lower the parallelism, as in `CMAKE_BUILD_PARALLEL_LEVEL=2 makepkg -si`
The 3D view shows “Rendering: QPainter (CPU) · simplified, OpenGL unavailable” at its top left	OpenGL 3.2 or later is unavailable. Check the GPU driver (`glxinfo -B` from `mesa-utils` shows the OpenGL implementation and version in use). It may be unavailable over remote desktops and in virtual machines
Rotation is slow although VTK draws	If `glxinfo -B` reports `llvmpipe` or similar, OpenGL is rendered in software
Japanese text shows as boxes	Install a Japanese font such as `noto-fonts-cjk`
With the Japanese interface, Qt’s standard dialogs such as file selection keep English text	Install `qt6-translations`
The pre-run check cannot find NWChem or the MPI launcher	Check `command -v nwchem mpirun` in a terminal. If NWChem is installed elsewhere, set its path in “3 Run settings”
It does not start, with `error while loading shared libraries`	A system update changed shared libraries. Make it again with `makepkg -sif` as in Updating

Verified configuration

On 2026-10-28, on Arch Linux (x86-64) with the configuration below, makepkg made the package from this PKGBUILD, its tests (the PKGBUILD’s check()) passed, and the package’s contents and dependencies were checked. The dependencies were installed with pacman, and makepkg’s check of the run-time and build-time dependencies passed.

Item	Version
Qt (`qt6-base`)	6.12.0
Open Babel	3.2.1
Eigen	5.0.1
RDKit, Boost	2026.09.1, 1.92.0
VTK	9.7.1
fast_float, nlohmann-json	8.3.2, 3.12.0
GCC, CMake, Ninja	16.2.1, 4.4.4, 1.13.2
NWChem (the AUR’s `nwchem`)	7.3.1
Open MPI	5.0.11

NWChem was started with mpirun -np 2 nwchem without a ~/.nwchemrc and completed an HF/6-31G* calculation of the hydrogen molecule. This was checked on a system with the dependencies already installed; installing the package with pacman (-i) and installing the dependencies automatically with makepkg -s and yay on a new system are not covered. The package’s executable, unpacked, was checked to start and to report version 1.0.0.