User Guide to Semiempirical Tight Binding

This user guide focuses on the semiempirical quantum mechanical methods GFNn-xTB, their descendants, and corresponding composite schemes as implemented in the xtb (extended tight binding) program package.

We provide a number of detailed guides dealing with common task that can be performed easily with the xtb program. All guides are usually structured the same way, starting with some simple examples using only the commandline and the default settings followed by a trouble shooting section. Detailed inputs are provided in a ready to use fashion to solve some more special but still common tasks with xtb together with some insights into the theory used behind the scences.

Recent developments, news and publications

  • 2021-08-27: QCxMS version 5.1.2 released by Jeroen Koopman

    This new update of the QCxMS program is linked against the AVX2 processor extension for increased performance. CID and EI runmode changes and bugfixes are implemented. The local run-script pqcxms was re-written and now performs better for parallel calculations.

    For a detailed description of all changes, check out the GitHub repository.

    QCxMS logo
  • 2021-08-06: QCxMS version 5.1.0 released by Jeroen Koopman

    This new update of the QCxMS program changes the way xtb is used inside the code. Instead of a standalone implementation of xtb version 5.8.1 in the source code, we switched to using the tblite library, which allows updates to the latest version of xtb. This, in return, leads to a significant increase in the computational speed of calculations done with the GFNn-xTB methods, while keeping the code independent from third party software.

    Furthermore, the PlotMS program has been updated as well.

    QCxMS logo
  • 2021-06-10: xtb version 6.4.1 released by Sebastian Ehlert

    We released a new version of xtb with a significantly improved memory footprint for large scale calculations and improved parallelisation for frequency calculations. The parallel evaluation of hessians with GFN-FF is now possible, overall we improved the stablility of the parallelisation which was slightly degraded in version 6.4.0. For xTB calculations the required OMP_STACKSIZE has been significantly reduced by restructuring the integral evaluation slightly.

    Also, this version of xtb now supports the COSMO/CPCM solvation model using the ddPCM library.

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  • 2021-06-10: QCxMS version 5.0.3 released by Jeroen Koopman

    Recently, we released the QCxMS program for calculating EI and CID mass spectra using molecular dynamics. The project moved to GitHub under the @qcxms namespace and will soon become an open source project, as soon as all major bugs are fixed.

    In this second update, we have started to update the output information provided by the program and especially the cid module and improved the way the automated general run-type of the CID module detemines the number of collisions. This in turn leads to a greater number of collisions in the simulation than in the versions before.

  • 2021-05-03: DFT-D4 version 3.2.0 released by Sebastian Ehlert

    We released a new version of DFT-D4 further expanding the functionality of the Python API and the integration with QCEngine and ASE. In this process we simplified the installation of the Python extension module which should now also be possible with pip. The DFT-D4 program can now also calculate pairwise resolved dispersion energies, both for the pairwise additive and pairwise non-additive contributions to the total dispersion energy.

    Find the complete release notes here.

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See the news archive for all posts.

xTB in Other Quantum Chemistry Programs

The xTB-methods are now officially available in other quantum chemistry programs!

  • in Orca 4.2 an IO-based interface to the xtb binary is available

  • AMS 2019 implements GFN1-xTB in their DFTB module

  • the entos program implements GFN1-xTB (also available in the webinterface)

  • the computational chemistry framework cuby4 supports xtb

  • Turbomole does support GFN1-xTB and GFN2-xTB since version 7.4

  • QCEngine supports calculations with the xtb API

  • the GMIN, OPTIM, and PATHSAMPLE global optimization tools provide a xtb interface

  • CP2K has an GFN1-xTB implementation since version 7.1

We missed your project here? No problem, just give us hint at the mailing list or open an issue at github.