charge_mode

This keyword allows one to specify the charge mode of a NEP4 potential model to be trained.

The syntax is:

charge_mode <mode_value>

where <mode_value> must be an integer that can assume one of the following values.

Value	Model description
0	original NEP without charge
1	qNEP model with charge, including both real- and reciprocal-space contributions
2	qNEP model with charge, including reciprocal-space contribution

Here, qNEP means NEP with charge (q). To train a qNEP model, we do not need to provide target charges. One can choose to provide target Born effective charges (BEC), but this usually only works for a single matter in a single phase, as we have assumed a constant high-frequency dielectric constant for the whole training dataset.