code: public static double predictIP(IAtomContainer container, IBond bond) throws CDKException {
          double value = 0;
  
          if (bond.getOrder().equals(IBond.Order.SINGLE)) return value;
  
          //if some of the atoms belongs to some of the heteroatom family than
          // it can not ionized
          for (int i = 0; i < 2; i++) {
              IAtom atom = bond.getAtom(i);
              if (familyHalogen(atom))
                  return value;
              else if (familyOxygen(atom))
                  return value;
              else if (familyNitrogen(atom)) return value;
          }
  
          if (!familyBond(container, bond)) return value;
  
          return getDTBondF(getQSARs(container, bond));
      }
docs: Method which is predict the Ionization Potential from given atom.
  
  @param container The IAtomContainer where is contained the IAtom
  @param bond      The IBond to prediction the IP
  @return          The value in eV