Use Jmol algorithm to determine bond length from atomic parameters
        Args:
            el1_sym: (str) symbol of atom 1
            el2_sym: (str) symbol of atom 2

        Returns: (float) max bond length

def get_max_bond_distance(self, el1_sym, el2_sym):
        """
        Use Jmol algorithm to determine bond length from atomic parameters
        Args:
            el1_sym: (str) symbol of atom 1
            el2_sym: (str) symbol of atom 2

        Returns: (float) max bond length

        """
        return sqrt(
            (self.el_radius[el1_sym] + self.el_radius[el2_sym] + self.tol) ** 2)