code: private double getElectrostaticPotentialN(IAtomContainer ac, int atom1, double[] ds) {
  
          //		double CoulombForceConstant = 1/(4*Math.PI*8.81/*Math.pow(10, -12)*/);
          double CoulombForceConstant = 0.048;
          double sum = 0.0;
          try {
              if (factory == null)
                  factory = AtomTypeFactory.getInstance("org/openscience/cdk/config/data/jmol_atomtypes.txt",
                          ac.getBuilder());
  
              List<IAtom> atoms = ac.getConnectedAtomsList(ac.getAtom(atom1));
              for (IAtom atom : atoms) {
                  double covalentradius = 0;
                  String symbol = atom.getSymbol();
                  IAtomType type = factory.getAtomType(symbol);
                  covalentradius = type.getCovalentRadius();
  
                  double charge = ds[STEP_SIZE * atom1 + atom1 + 5];
                  logger.debug("sum_(" + sum + ") = CFC(" + CoulombForceConstant + ")*charge(" + charge + "/ret("
                          + covalentradius);
                  sum += CoulombForceConstant * charge / (covalentradius * covalentradius);
              }
          } catch (CDKException e) {
              logger.debug(e);
          }
  
          return sum;
      }
docs: get the electrostatic potential of the neighbours of a atom.
  
  @param ac   The IAtomContainer to study
  @param ds
  @param atom1 The position of the IAtom to study
  @return     The sum of electrostatic potential of the neighbours