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.
Quick Links¶
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.
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.
2021-06-10: xtb version 6.4.1 released by Sebastian Ehlert
We released a new version of
xtbwith 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 requiredOMP_STACKSIZEhas been significantly reduced by restructuring the integral evaluation slightly.Also, this version of
xtbnow supports the COSMO/CPCM solvation model using the ddPCM library.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.
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
xtbbinary is availableAMS 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
xtbTurbomole does support GFN1-xTB and GFN2-xTB since version 7.4
QCEngine supports calculations with the
xtbAPIthe GMIN, OPTIM, and PATHSAMPLE global optimization tools provide a
xtbinterfaceCP2K 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.
Quickstart
Guides
- Singlepoint Calculations
- Properties
- Geometry Optimization
- Exploration of the potential energy surface (PES)
- Implicit Solvation
- Calculation of Vibrational Frequencies
- Molecular Dyamics Simulations
- Meta-Dynamics Simulations
- Reaction Path Methods
- Growing String Method
- Periodic Boundary Conditions
- External Potentials and Embedding
- GFN-Force-Field (GFN-FF)
- C API to the extended tight binding program
- Python Integration for the xtb API
- Community resources
Submodules
CREST
- Introduction to CREST
- CREST Versions and Changelog
- CREST command line arguments
- Example applications
- iMTD-GC conformational search
- Sorting an ensemble
- Comparing two ensembles
- Constrained conformational sampling
- Sampling of noncovalent complexes and aggregates (NCI mode)
- Molecular prototropy screening
- Property calculations on final ensemble
- Dry run to check settings prior to calculations
- Examples from the paper: Automated exploration of the low-energy chemical space with fast quantum chemical methods
- Preparing a Nanoreactor calculation for
xtb
- Quantum Cluster Growth
ENSO
CENSO
- Introduction to CENSO
- Setting up CENSO
- Censorc keyword definitions
- Thresholds
- Solvation
- NMR
- Trouble shooting
- Usage examples
- Calculate fast DFT(B97-D3(0)/def2-SV(P)+gcp) single-point energies on GFNn-xTB input geometries
- Calculate free energies in solution phase (CHCl3) on GFNn-xTB geometries
- Calculate free energies on populated, DFT optimized conformers
- Calculation of NMR spectra
- Calculation of optical rotation
- Restarting calculations
- Abbreviations