Prioritize GAV thermo estimates by number of aromatic rings

Group values are often fitted to the most aromatic resonance
structure of a molecule. This can cause issues if the thermo
value for a less representative structure ends up being lower
than that of the aromatic structure, even though it has a more
accurate group estimate.

This approach ensures more predictable behavior after adding
new group values for aromatic species.

Author: mliu49

rmgpy/data/thermo.py

@@ -1785,17 +1785,22 @@ def prioritize_thermo(self, species, thermo_data_list):
             if species.molecule[0].is_cyclic():
                 # Special treatment for cyclic compounds
                 entries = []
-                for thermo in thermo_data_list:
+                for i, thermo in enumerate(thermo_data_list):
                     ring_groups, polycyclic_groups = self.get_ring_groups_from_comments(thermo)
 
                     # Use rank as a metric for prioritizing thermo. 
                     # The smaller the rank, the better.
                     sum_rank = np.sum(
                         [3 if entry.rank is None else entry.rank for entry in ring_groups + polycyclic_groups])
-                    entries.append((thermo, sum_rank))
 
-                # Sort first by rank, then by enthalpy at 298 K
-                entries = sorted(entries, key=lambda entry: (entry[1], entry[0].get_enthalpy(298.)))
+                    # Also use number of aromatic rings as a metric, more aromatic rings is better
+                    # Group values are generally fitted to the most aromatic resonance structure
+                    num_arom_rings = species.molecule[i].count_aromatic_rings()
+
+                    entries.append((thermo, sum_rank, -num_arom_rings))
+
+                # Sort first by number of aromatic rings, then rank, then by enthalpy at 298 K
+                entries = sorted(entries, key=lambda entry: (entry[2], entry[1], entry[0].get_enthalpy(298.)))
                 indices = [thermo_data_list.index(entry[0]) for entry in entries]
             else:
                 # For noncyclics, default to original algorithm of ordering thermo based on the most stable enthalpy