Installation

General Considerations

The xtb software is open-source and available under the LGPL 3.0 license on GitHub. This guide provides a brief summary of the official installation guide.

If you encounter any issues, refer to the full documentation or open an issue on GitHub for support.

Warning: The primary operating system (OS) for developing and using xtb is Linux. While installation on Windows and macOS is possible, support for these platforms may be more limited.

Easy Installation

The simplest way to install xtb is by downloading the precompiled binaries. There, you have also access a bleeding-edge version of the program.

After downloading the appropriate version, extract the files, make them executable, and add the program to your PATH variable for easy access:

tar -xvf xtb*.tar.xz
chmod +x ./xtb-dist/bin/xtb
export PATH=$PWD/xtb-dist/bin:$PATH

Alternatively, you can copy the xtb binary to a directory of your choice, e.g., your bin folder.
To verify that the executable is correctly linked, use:

which xtb

And check the installed version with:

xtb --version

Tip: You can add the full path to your xtb executable to the Bash shell configuration file (~/.bashrc) to automatically load xtb in new sessions.

Homebrew Support

xtb can also be installed with Homebrew. The support is provided by an additional GitHub repository that provides access also to additional software. xtb can be installed on MacOS via

brew tap grimme-lab/qc
brew install xtb

Important settings

To work properly also for large systems, it is recommended to unlimit the system stack size, e.g., with bash by:

ulimit -s unlimited

This can also be included in the ~/.bashrc file.

Further, to allow parallelisation, a reasonable large number of OMP stacksize must be provided, e.g.:

export OMP_STACKSIZE=4G

and the number of cores to be used by xtb are set with

export OMP_NUM_THREADS=<ncores>,1

Compilation

A more advanced approach is to compile xtb from source. Native compilation offers several advantages over precompiled binaries, such as generating a system-optimized binary and enabling in-place modifications to the software.

This guide follows a minimalistic build process using the default toolchain: the meson build system and the ifort/icc compilers.

First step is to clone the official GitHub repository via:

git clone https://github.com/grimme-lab/xtb.git

Then, define the Fortran and C compilers, which can be installed via Intel’s Developer Toolkit:

export FC=ifort CC=icc

Finally, you can build the project with Meson:

meson setup build --buildtype=release
meson compile -C build

Alternatively, gfortran/gcc compilers are also supported. For a complete list of supported compilers and backends, please see the github page.