Updated behaviour

Author: calvinp0

arc/statmech/arkane.py

@@ -886,11 +886,10 @@ def _find_best_level_key_for_sp_level(level: "Level",
             best_key = lot_str
             break
 
-        # No target year specified: pick the latest year if present, otherwise fall back to no-year entry.
+        # No target year specified: prefer no-year entry; if absent, pick latest year.
         if cand_year is None:
-            if best_year is None:
-                best_key = lot_str
-            continue
+            best_key = lot_str
+            break
 
         if best_year is None or cand_year > best_year:
             best_year = cand_year

arc/statmech/arkane_test.py

@@ -146,7 +146,7 @@ def test_get_arkane_model_chemistry(self):
                          "LevelOfTheory(method='ccsd(t)f12',basis='ccpvtzf12',software='molpro')")
         self.assertEqual(get_arkane_model_chemistry(sp_level=Level(method='CBS-QB3'),
                                                     freq_scale_factor=1.0),
-                         "LevelOfTheory(method='cbsqb32023',software='gaussian')")
+                         "LevelOfTheory(method='cbsqb3',software='gaussian')")
 
     def test_get_arkane_model_chemistry_year_not_found(self):
         """Test warnings when a requested year is not found in the Arkane database."""
@@ -160,7 +160,7 @@ def test_get_arkane_model_chemistry_latest_year(self):
         """Test selecting the latest available year when no year is specified."""
         model_chemistry = get_arkane_model_chemistry(sp_level=Level(method='CBS-QB3'),
                                                      freq_scale_factor=1.0)
-        self.assertEqual(model_chemistry, "LevelOfTheory(method='cbsqb32023',software='gaussian')")
+        self.assertEqual(model_chemistry, "LevelOfTheory(method='cbsqb3',software='gaussian')")
 
     def test_generate_arkane_input(self):
         """Test generating Arkane input"""

docs/source/advanced.rst

@@ -108,7 +108,8 @@ Equivalent ``input.yml`` form::
       basis: def2tzvp
       year: 2023
 
-If ``year`` is omitted, ARC will match the newest available entry for that method/basis in the Arkane database.
+If ``year`` is omitted, ARC will prefer the no-year Arkane entry for that method/basis. If none exists,
+ARC will fall back to the latest available year in the Arkane database.
 
 
 The following are examples for **equivalent** definitions::

docs/source/examples.rst

@@ -87,6 +87,8 @@ To specify a composite method, simply define something like::
 Note: Do not include year suffixes in ``level_of_theory`` (e.g., ``wb97xd32023``). Year suffixes are
 for Arkane database matching only and are not valid QC methods. If you need a specific correction year,
 set ``arkane_level_of_theory`` with a ``year`` value instead.
+If ``year`` is omitted, ARC will prefer the no-year Arkane entry for that method/basis; if none exists,
+ARC will fall back to the latest available year in the Arkane database.
 
 Note that for composite methods the ``freq_level`` and ``scan_level`` may have different
 default values than for non-composite methods (defined in settings.py). Note: an independent