Returns the charge transferred for a particular atom. Requires POTCAR
        to be supplied.

        Args:
            atom_index:
                Index of atom.

        Returns:
            Charge transfer associated with atom from the Bader analysis.
            Given by final charge on atom - nelectrons in POTCAR for
            associated atom.

def get_charge_transfer(self, atom_index):
        """
        Returns the charge transferred for a particular atom. Requires POTCAR
        to be supplied.

        Args:
            atom_index:
                Index of atom.

        Returns:
            Charge transfer associated with atom from the Bader analysis.
            Given by final charge on atom - nelectrons in POTCAR for
            associated atom.
        """
        if self.potcar is None:
            raise ValueError("POTCAR must be supplied in order to calculate "
                             "charge transfer!")
        potcar_indices = []
        for i, v in enumerate(self.natoms):
            potcar_indices += [i] * v
        nelect = self.potcar[potcar_indices[atom_index]].nelectrons
        return self.data[atom_index]["charge"] - nelect