Fast approximate DFT for molecules, surfaces and bulk materials
Density-Functional based Tight-Binding (DFTB) allows to perform calculations of large systems over long timescales even on a desktop computer. Relatively accurate results are obtained at a fraction of the cost of density functional theory (DFT) by using pre-calculated parameters, a minimal basis, and including only nearest-neighbor interactions. Long-range interactions are described with empirical dispersion corrections, while third-order corrections accurately handle charged systems. With full integration into the AMS driver, the DFTB module can be combined with all AMS-driver functionality, e.g. Molecular Dynamics, Monte Carlo or PES exploration.
The DFTB module can treat molecular as well as periodic systems (1D for nanotubes, 2D for surfaces, 3D for bulk), and as such can be used as a fast pre-optimizer for full molecular and periodic DFT calculations with ADF and BAND. The DFTB license also includes the semi-empirical MOPAC library, which uses similar approximations and is parametrized against experimental heats of formations. From on AMS2019, Prof. Grimme’s GFN1-xTB method which is parametrized for most elements of the periodic table is included. To further increase the accuracy of the xTB model for specific applications, we have added the option to refit xTB parameters using our dedicated ParAMS parametrization suite.
With the integrated graphical user interface it is easy to run, set up and analyze DFTB jobs, or to use DFTB as a quick pre-optimization tool.
Like DFTB, the semi-empirical MOPAC code uses the nearest neighbor and minimal basis set approximations, making it fast and linear scaling. MOPAC has been parametrized against an enormous set of thoroughly examined experimental data, in a huge, commendable effort by Dr. Jimmy Stewart. The latest parametrization set (PM7) is also the most accurate. Since AMS2019, the MOPAC and DFTB modules are now bundled together and only one license is needed to use both methods.
