Return the intrinsic pore diameter.

        Returns
        -------
        :class:`float`
            The intrinsic pore diameter.

def calculate_pore_diameter(self):
        """
        Return the intrinsic pore diameter.

        Returns
        -------
        :class:`float`
            The intrinsic pore diameter.

        """
        self.pore_diameter, self.pore_closest_atom = pore_diameter(
            self.elements, self.coordinates)
        self.properties['pore_diameter'] = {
            'diameter': self.pore_diameter,
            'atom': int(self.pore_closest_atom),
        }
        return self.pore_diameter