# Introduction¶

This document is a collection of examples demonstrating the usage of the atomistic quantum mechanical software DFTB+.

## Before you start¶

The examples assume that you have the latest stable version of DFTB+ installed (although many of the recipes may also work with older versions of the code). Additionally the examples require some parameterisation files (Slater-Koster files), which can be downloaded from dftb.org.

The recipes in this document often only show the relevant parts of the input. In order to obtain the full input files and in order to run the examples yourself, please download the archive containing all the inputs of the individual recipes.

Download archive with all inputs.

In each recipe we indicate where to find the corresponding directories in the archive with square brackets after the section title (e.g. [Input: recipes/basics/firstcalc/]).

### Installing from conda-forge¶

DFTB+ is available with the cross platform package manager conda on the conda-forge channel. If you have no conda installation yet, we recommend to bootstrap an installation with the conda-forge distribution miniforge or the anaconda distribution miniconda.

Installing dftb+ 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, dftb+ can be installed with:

conda install dftbplus


If you prefer to install an MPI parallel version you have to explicitly request it with

conda install 'dftbplus=*=mpi_*'


Additional components, like the dptools and the Python API, are available as separate packages on the same channel. You can install them with

conda install dftbplus-tools dftbplus-python


It is possible to list all of the versions of dftb+ and its additional components available on your platform with:

conda search 'dftbplus*' --channel conda-forge


### Getting Slater-Koster data¶

After unpacking the archive, you must also download all Slater-Koster-files needed by the examples, by using the supplied script as

./scripts/get_slakos


in the root folder of the archive. You should then be able to run each example by calling dftb+ from the corresponding input folder (assuming that dftb+ is installed in your executable path). For some examples, there is also a supplied script file in the directory to run examples of multistage calculations, called run.sh which contains the individual commands needed to run the full example.

## Where to start¶

The individual chapters are more or less independent from each other, so you may go directly to the one relevant to your interests. However, if you are new to DFTB+, please make sure to work through the relevant introductory examples in the Basic usage chapters first.

The recipes are to introduce you to specific functionalities of DFTB+ and so are, therefore rather short and focused. Please also always consult the corresponding sections of the DFTB+ manual for further details and possibilities.

Please note that the example outputs in the recipes may have been created with older versions of DFTB+ and therefore could differ slightly in format from output of the most recent code. The corresponding inputs in the archive should work, without any changes, with the last stable release of DFTB+.