Installation

Table of contents

1. General Considerations
2. Straighforward Installation
3. Compilation
4. External Driver Programs
5. Utility Tools

General Considerations

The xtb software is open-source and available under the LGPL 3.0 license on the GitHub platform. This guide provides a brief summary of the existing guideline. Some features are available only for the newer version of xtb (=6.7.0, start Linux download). In case of any issues, you can always refer to the full documentation for further details. Even though xtb is cross-platform, for simplicity and stability reasons, we assume a Linux distribution for the rest of the workshop.

Straighforward Installation

The most straightforward way to install xtb is by downloading the precompiled binaries. You can also get bleeding-edge version of the program. After downloading the appropriate version, extract it, make it executable, and add it to your PATH variable:

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

To verify that the executable is correctly linked, use:

which xtb

And check the installed version with:

xtb --version

Compilation

A more advanced approach is to compile xtb from the source code. Native compilation has certain advantages over precompiled binaries, such as producing a system-tailored binary and allowing modifications to the software in place.

Here, we follow a minimalistic build using our 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

External Driver Programs

During the workshop, we will use external programs, namely Conformer–Rotamer Ensemble Sampling Tool (CREST) and Command-line Energetic Sorting (CENSO). Note that CENSO is only required in the optional 6th exercise. The simplest way to install CREST is by downloading the precompiled binaries, similar to xtb. Full installation instructions can be found here. The installation instructions for CENSO can be found in the official project repository.

Utility Tools

During the course of the workshop, you will also need to visualize molecular structures. The required graphical user interfaces (GUIs) include Avogadro, Molden, Chimerax and others. Additionally, you should have a text editor (e.g., vim, nano, VSCode) to edit input files and adjust calculation parameters as needed.