Database

The database keywords are documented here: https://www.nextnano.com/documentation/tools/nextnano3/database/keywords/

The database contains the material parameters, e.g. see also section How to input material parameters.
The parameters of the materials will be read in via the database database_nn3.in. This is the place where you can change material data in case you want to. Alternatively, you can overwrite default material parameters by adding them to your input file.