Semiempirical Extended Tight-Binding Program Package

This is the official repository of the xtb program package developed by the Grimme group in Bonn.

Table of Contents

• Installation
  • Meson
  • CMake
  • Conda
• Documentation
• Contributing
• Citations
• License

Installation

Statically linked binaries are provided on the latest release page, and bleeding-edge static binaries (as well as the source distribution archive) built from the latest main branch are available on the continuous release tag (bleed) for five platforms:

• Linux (x86_64, compiled with Intel oneAPI ifx/icx and MKL; aarch64, compiled with GCC and OpenBLAS)
• macOS (arm64 and x86_64, compiled with GCC and OpenBLAS)
• Windows (x86_64, compiled with MinGW-w64 UCRT64 GCC and OpenBLAS)

The xtb program and library are also packaged on conda-forge for Linux (x86_64, aarch64, ppc64le) and macOS (x86_64, arm64). For Homebrew users a custom tap is available at grimme-lab/homebrew-qc providing prebuilt macOS/x86_64 binaries; for macOS/arm64, binaries will be compiled on installation automatically.

This project supports two build systems, meson and CMake. A short guide on the usage of each is given here, follow the linked instructions for more detailed information (meson guide, CMake guide).

Compilers:

1. ifx, icx, icpx
2. gfortran, gcc, g++
3. ifort (<=2021.10.0), icc (<=2021.10.0)

Known issues with combinations:

1. GCC-13 + MacOS + AArch64

Meson

Using meson as build system requires you to install a fairly new version like 0.62 or newer (except 1.8.0 and 1.8.1). To use the default backend of meson you have to install ninja version 1.7 or newer.

export FC=ifx CC=icx
meson setup build --buildtype release --optimization 2
ninja -C build test

Important

Compilation with meson on macOS differs slightly from the protocol for Linux-based systems. Different BLAS libraries can lead to deviating results in rare cases – please stick to the following instructions.

Setting up meson on macOS

Compiling with meson on macOS

1. Use Homebrew for Package Management: Install dependencies like gcc, gfortran, and openblas using Homebrew. Further information on how to setup brew. Example:

   brew install gcc gfortran openblas

2. meson setup call with appropriate environment variables: Use the following adapted meson setup call to compile xtb on macOS (adjusting the OpenBLAS path and the installed Homebrew compiler version, e.g., gfortran-14/gcc-14, for your system).

   LDFLAGS="-L/opt/homebrew/opt/openblas/lib" CPPFLAGS="-I/opt/homebrew/opt/openblas/include" FC=gfortran-14 CC=gcc-14 meson setup _build --buildtype release -Dlapack=openblas

Make sure the testsuite is running without errors.

To install the xtb binaries to /usr/local use (might require sudo)

ninja -C build install

For more information on the build with meson see the instructions here.

CMake

The CMake build system requires both make and CMake to be installed, the latter has to be version 3.18 or newer.

Building xtb with CMake works with the following chain of commands:

cmake -B build -DCMAKE_BUILD_TYPE=Release
make -C build
make -C build test

To install the xtb binaries to /usr/local use (might require sudo)

make -C build install

For more detailed information on the build with CMake see the instructions here.

Conda

Installing xtb from the conda-forge channel can be achieved by adding conda-forge to your channels with:

conda config --add channels conda-forge

Once the conda-forge channel has been enabled, xtb can be installed with:

conda install xtb

It is possible to list all of the versions of xtb available on your platform with:

conda search xtb --channel conda-forge

Documentation

The xtb documentation is hosted at read-the-docs.

Contributing

Please read our contributing guidelines before contributing to this project.

Contributors

We are developing this program to make our research possible. Many of the features that xtb has today have been added because there was a dire need for them and we had many contributors who made these features reality:

• P. Atkinson (@patrickatkinson)
• T. Balduf (@TyBalduf)
• C. Bannwarth (@cbannwarth)
• F. Bohle (@fabothch)
• G. Brandenburg (@gbrandenburg)
• E. Caldeweyher (@f3rmion)
• M. Checinski
• S. Dohm (@thch-dohm)
• S. Ehlert (@awvwgk)
• S. Ehrlich
• M. Friede (@marvinfriede)
• T. Froitzheim (@thfroitzheim)
• I. Gerasimov (@foxtran)
• J. Gorges (@gorges97)
• S. Grimme (@stefangrimme)
• C. Hölzer (@hoelzerC)
• A. Katbashev (@Albkat)
• J. Kohn (@demonic-daisy)
• J. Koopman (@JayTheDog)
• C. Lavigne (@clavigne)
• S. Lehtola (@susilehtola)
• F. März
• M. Müller (@marcelmbn)
• F. Musil (@felixmusil)
• H. Neugebauer (@haneug)
• J. Pisarek
• C. Plett (@cplett)
• P. Pracht (@pprcht)
• F. Pultar (@pultar)
• T. Rose (@Thomas3R)
• J. Seibert (@liljay42)
• L. M. Seidler (@lmseidler)
• C. E. Selzer (@chselz)
• P. Shushkov
• S. Spicher (@sespic)
• M. Stahn (@MtoLStoN)
• M. Steiner (@steinmig)
• T. Strunk (@timostrunk)
• J. Stückrath (@jbstueckrath)
• J. Unsleber (@nabbelbabbel)

Contributors are listed in alphabetical order. Some contributions predate the GitHub release of this project and are not visible in the repository commit history. For the contributor data from the commit history since then look here.

Citations

General Reference to xtb and the implemented GFN methods:

• C. Bannwarth, E. Caldeweyher, S. Ehlert, A. Hansen, P. Pracht, J. Seibert, S. Spicher, S. Grimme WIREs Comput. Mol. Sci., 2021, 11, e1493. DOI: 10.1002/wcms.1493

for the xtb software:

• A. Katbashev, M. Stahn, T. Rose, V. Alizadeh, M. Friede, C. Plett, P. Steinbach, S. Ehlert, J. Phys. Chem. A, 2025, 129, 2667–2682. DOI: 10.1021/acs.jpca.4c08263

for GFN-xTB:

• S. Grimme, C. Bannwarth, P. Shushkov, J. Chem. Theory Comput., 2017, 13, 1989-2009. DOI: 10.1021/acs.jctc.7b00118
• C. Bannwarth, S. Ehlert and S. Grimme., J. Chem. Theory Comput., 2019, 15, 1652-1671. DOI: 10.1021/acs.jctc.8b01176
• P. Pracht, E. Caldeweyher, S. Ehlert, S. Grimme, ChemRxiv, 2019, preprint. DOI: 10.26434/chemrxiv.8326202.v1

for spGFNn-xTB (spin-polarization):

• H. Neugebauer, B. Bädorf, S. Ehlert, A. Hansen, S. Grimme, J. Comput. Chem., 2023, 44, 2120–2129. DOI: 10.1002/jcc.27185

for GFN-FF:

• S. Spicher and S. Grimme, Angew. Chem. Int. Ed., 2020, 59, 15665–15673 DOI: 10.1002/anie.202004239
• T. Rose, M. Bursch, J.-M. Mewes, S. Grimme, Inorg. Chem., 2024, 63, 19364–19374. DOI: 10.1021/acs.inorgchem.4c03215

for periodic GFN-FF (mcGFN-FF):

• S. Grimme and T. Rose, Z. Naturforsch. B, 2024, 79, 191–200. DOI: 10.1515/znb-2023-0088

for PTB:

• S. Grimme, M. Müller, A. Hansen, J. Chem. Phys. 2023, 158, 124111. DOI: 10.1063/5.0137838

for CEH:

• M. Müller, T. Froitzheim, A. Hansen, S. Grimme, J. Phys. Chem. A, 2024, 128, 10723–10736. DOI: 10.1021/acs.jpca.4c06989

for GBSA and ALPB implicit solvation:

• S. Ehlert, M. Stahn, S. Spicher, S. Grimme, J. Chem. Theory Comput., 2021, 17, 4250-4261 DOI: 10.1021/acs.jctc.1c00471

for CPCM-X implicit solvation:

• M. Stahn, S. Ehlert, S. Grimme, J. Phys. Chem. A, 2023, 127, 7036–7043. DOI: 10.1021/acs.jpca.3c04382

for ddX implicit solvation:

• M. Nottoli, M. F. Herbst, A. Mikhalev, A. Jha, F. Lipparini, B. Stamm, WIREs Comput. Mol. Sci., 2024, 14, e1726. DOI: 10.1002/wcms.1726

for DFT-D4:

• E. Caldeweyher, C. Bannwarth and S. Grimme, J. Chem. Phys., 2017, 147, 034112. DOI: 10.1063/1.4993215
• E. Caldeweyher, S. Ehlert, A. Hansen, H. Neugebauer, S. Spicher, C. Bannwarth and S. Grimme, J. Chem. Phys., 2019, 150, 154122. DOI: 10.1063/1.5090222
• E. Caldeweyher, J.-M. Mewes, S. Ehlert and S. Grimme, Phys. Chem. Chem. Phys., 2020, 22, 8499-8512. DOI: 10.1039/D0CP00502A
• L. Wittmann, I. Gordiy, M. Friede, B. Helmich-Paris, S. Grimme, A. Hansen and M. Bursch, Phys. Chem. Chem. Phys., 2024, 26, 21379-21394. DOI: 10.1039/D4CP01514B

for sTDA-xTB:

• S. Grimme and C. Bannwarth, J. Chem. Phys., 2016, 145, 054103. DOI: 10.1063/1.4959605

for FOD:

• S. Grimme and A. Hansen, Angew. Chem. Int. Ed., 2015, 54, 12308–12313. DOI: 10.1002/anie.201501887
• C. A. Bauer, A. Hansen, S. Grimme, Chem. Eur. J., 2017, 23, 6150–6164. DOI: 10.1002/chem.201604682

in the mass-spec context:

• V. Asgeirsson, C. Bauer and S. Grimme, Chem. Sci., 2017, 8, 4879. DOI: 10.1039/c7sc00601b
• J. Koopman and S. Grimme, ACS Omega, 2019, 4, 12, 15120-15133. DOI: 10.1021/acsomega.9b02011
• J. Koopman and S. Grimme, J. Am. Soc. Mass Spectrom., 2021, 32, 7, 1735-1751. DOI: 10.1021/jasms.1c00098
• J. Gorges and S. Grimme, Phys. Chem. Chem. Phys., 2025, 27, 6899-6911. DOI: 10.1039/D5CP00316D

for metadynamics refer to:

• S. Grimme, J. Chem. Theory Comput., 2019, 15, 2847-2862. DOI: 10.1021/acs.jctc.9b00143

for SPH calculations refer to:

• S. Spicher and S. Grimme, J. Chem. Theory Comput., 2021, 17, 1701–1714. DOI: 10.1021/acs.jctc.0c01306

for ONIOM refer to:

• C. Plett, A. Katbashev, S. Ehlert, S. Grimme, M. Bursch, Phys. Chem. Chem. Phys., 2023, 25, 17860-17868. DOI: 10.1039/D3CP02178E

for DIPRO refer to:

• J. T. Kohn, N. Gildemeister, S. Grimme, D. Fazzi, A. Hansen, J. Chem. Phys., 2023, 159, 144106. DOI: 10.1063/5.0167484

for O1NumHess refer to:

• B. Wang, S. Luo, Z. Wang, W. Liu, J. Chem. Theory Comput., 2025, 21, 10893-10909. DOI: 10.1021/acs.jctc.5c01354

All references are available in bibtex format.

License

xtb is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

xtb is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU Lesser General Public License for more details.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in xtb by you, as defined in the GNU Lesser General Public license, shall be licensed as above, without any additional terms or conditions.