This WaNo allows the users to perform periodic DFT calculations using the VASP code without requiring a deep understanding of VASP's functionalities and input files. The user can choose between single point calculations, structure optimisations, ab-initio MD and NEB calculations. Electronic DOS and band structure calculations are also possible, for which it is recommended to use this WaNo several times in a corresponding workflow. The mandatory input of this WaNo consists only of a structure file in POSCAR format (except for NEB calculations), and all other input files can be created automatically.

The code is based on python and the necessary virtual environment on the server is provided by Simstack. In addition, a configuration file called vasp.config needs to be provided in $NANOMATCH/$NANOVER/configs on the server where the environment variable $NANOVER can be adjusted in the xml file. The config file is responsible for setting up the VASP environment on the cluster which can be done by loading a corresponding module or by defining all necessary environment variables. In addition some WaNo-specific variables must be set to define the necessary commands and paths (see vasp.config for an example).

The only required input is an initial structure in POSCAR format.

• VASP version
  The chosen version must be available on the compute cluster. Please adjust the xml and vasp.config files accordingly.

• Structure file This is the only mandatory input (except for NEB calculations; see above), and the structure must be given in POSCAR format.

• Plane waves file
  The user can choose between uploading a suitable POTCAR file or to rely on of the default. If the chosen PAW type is not available for a given element, the WaNo automatically looks for an alternative.

• K-sampling
  Different options are possible, with default being to define the minimum distance between two k-points in reciprocal space.

• Electronic structure settings
  Here, the parameters of DFT calculation are set up. Please check the VASP manual for further information on the different options. If a vDW functional is chosen, the vdw_kernel.bindat file must additionally be provided.

• NEB settings
  In case of a NEB calculation the user must provide either the initial and final structure of the path, so that the WaNo can linearly interpolate in order to create the starting images. Alternatively, a tar file can be provided which must contain folders 00 to xx containg each a starting image file named POSCAR.

• *Output files
  Check the corresponding boxes if the CHGCAR and WAVECAR files are to be reused for analysis or restarting a calculation, otherwise empty files will be written.

The output of this WaNo consists of the VASP ouput files CONTCAR, CHGCAR, WAVECAR as well as IBZKPT. In addition, an archive file with all relevant output files is written. The file output_dict.yml contains information about snapshots of an MD calculation and is empty otherwise.