Approximate Cp0 and CpInf for adsorbed species.

See cfgoldsmith#5
for more detailed version.

Heat capacity for surface species is 0.01 not 0.
Absolute 0 causes problem.

rmgpy/molecule/molecule.py

@@ -1768,6 +1768,8 @@ def calculateCp0(self):
         """
         Return the value of the heat capacity at zero temperature in J/mol*K.
         """
+        if self.containsSurfaceSite():
+            return 0.01
         if len(self.atoms) == 1:
             return 2.5 * constants.R
         else:
@@ -1779,10 +1781,13 @@ def calculateCpInf(self):
         """
         cython.declare(Natoms=cython.int, Nvib=cython.int, Nrotors=cython.int)
 
+        if self.containsSurfaceSite():
+            # ToDo: internal rotors could still act as rotors
+            return constants.R * 3 * len(self.vertices)
+
         if len(self.vertices) == 1:
             return self.calculateCp0()
         else:
-
             Natoms = len(self.vertices)
             Nvib = 3 * Natoms - (5 if self.isLinear() else 6)
             Nrotors = self.countInternalRotors()