The program reads this cif keyword in as the atom's force_field_type, despite it not being designed for that intended purpose. In cases where some random string is put here such as 'Cu0', the program will try to find the appropriate force-field type in one of the force field dictionaries. Eg. UFF has 'Cu3+2' so a KeyError is raised when searching for 'Cu0'.
The program reads this cif keyword in as the atom's force_field_type, despite it not being designed for that intended purpose. In cases where some random string is put here such as 'Cu0', the program will try to find the appropriate force-field type in one of the force field dictionaries. Eg. UFF has 'Cu3+2' so a KeyError is raised when searching for 'Cu0'.