code: @Override
      public DescriptorValue calculate(IAtom atom, IAtomContainer container) {
          String symbol = atom.getSymbol();
          double vdwradius = PeriodicTable.getVdwRadius(symbol);
          return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(),
                  new DoubleResult(vdwradius), NAMES);
  
      }
docs: This method calculate the Van der Waals radius of an atom.
  
  @param  container         The {@link IAtomContainer} for which the descriptor is to be calculated
  @return                   The Van der Waals radius of the atom