Draft: Fixed issues in the Formula class, added tests, improved the description of formulas.

Closes #1259 (closed)

nomad/datamodel/results.py

@@ -1035,8 +1035,9 @@ class System(MSection):
     formula_hill = Quantity(
         type=str,
         description='''
-            The chemical formula for a structure in Hill form with element symbols followed by
-            integer chemical proportion numbers. The proportion number MUST be omitted if it is 1.
+            The chemical formula for a structure in Hill form with element
+            symbols followed by non-reduced integer chemical proportion numbers.
+            The proportion number is omitted if it is 1.
         ''',
         a_elasticsearch=[
             Elasticsearch(material_type, normalizer=atomutils.get_formula_hill),
@@ -1046,8 +1047,8 @@ class System(MSection):
     formula_reduced = Quantity(
         type=str,
         description='''
-            The reduced chemical formula for a structure as a string with element symbols and
-            integer chemical proportion numbers. The proportion number MUST be omitted if it is 1.
+            Alphabetically sorted chemical formula with reduced integer chemical
+            proportion numbers. The proportion number is omitted if it is 1.
         ''',
         a_elasticsearch=[
             Elasticsearch(material_type),
@@ -1057,10 +1058,10 @@ class System(MSection):
     formula_anonymous = Quantity(
         type=str,
         description='''
-            The anonymous formula is the chemical_formula_reduced, but where the elements are
-            instead first ordered by their chemical proportion number, and then, in order left to
-            right, replaced by anonymous symbols A, B, C, ..., Z, Aa, Ba, ..., Za, Ab, Bb, ... and
-            so on.
+            Formula where the elements are ordered by their reduced chemical
+            proportion number, and then, in order left to right, replaced by
+            anonymous symbols A, B, C, ..., Z, Aa, Ba, ..., Za, Ab, Bb, ... and
+            so on. The proportion number is omitted if it is 1.
         ''',
         a_elasticsearch=[
             Elasticsearch(material_type),
@@ -1233,8 +1234,8 @@ class Material(MSection):
     chemical_formula_reduced = Quantity(
         type=str,
         description='''
-            The reduced chemical formula for a structure as a string with element symbols and
-            integer chemical proportion numbers. The proportion number MUST be omitted if it is 1.
+            Alphabetically sorted chemical formula with reduced integer chemical
+            proportion numbers. The proportion number is omitted if it is 1.
         ''',
         a_elasticsearch=[
             Elasticsearch(material_type),
@@ -1244,8 +1245,9 @@ class Material(MSection):
     chemical_formula_hill = Quantity(
         type=str,
         description='''
-            The chemical formula for a structure in Hill form with element symbols followed by
-            integer chemical proportion numbers. The proportion number MUST be omitted if it is 1.
+            The chemical formula for a structure in Hill form with element
+            symbols followed by non-reduced integer chemical proportion numbers.
+            The proportion number is omitted if it is 1.
         ''',
         a_elasticsearch=[
             Elasticsearch(material_type, normalizer=atomutils.get_formula_hill),
@@ -1255,10 +1257,10 @@ class Material(MSection):
     chemical_formula_anonymous = Quantity(
         type=str,
         description='''
-            The anonymous formula is the chemical_formula_reduced, but where the elements are
-            instead first ordered by their chemical proportion number, and then, in order left to
-            right, replaced by anonymous symbols A, B, C, ..., Z, Aa, Ba, ..., Za, Ab, Bb, ... and
-            so on.
+            Formula where the elements are ordered by their reduced chemical
+            proportion number, and then, in order left to right, replaced by
+            anonymous symbols A, B, C, ..., Z, Aa, Ba, ..., Za, Ab, Bb, ... and
+            so on. The proportion number is omitted if it is 1.
         ''',
         a_elasticsearch=[
             Elasticsearch(material_type),