Clarified the meaning of number_of_atoms and atom_positions for the case of alloys.

meta_info/nomad_meta_info/public.nomadmetainfo.json

@@ -104,7 +104,7 @@
         "configuration_core"
       ]
     }, {
-      "description": "Positions of all the atoms, in Cartesian coordinates. This metadata defines a configuration and is therefore required.",
+      "description": "Positions of all the atoms, in Cartesian coordinates. This metadata defines a configuration and is therefore required. For alloys where concentrations of species are given for each site in the unit cell, it stores the position of the sites.",
       "dtypeStr": "f",
       "name": "atom_positions",
       "shape": [
@@ -1880,7 +1880,7 @@
         "section_atom_projected_dos"
       ]
     }, {
-      "description": "Stores the total number of atoms used in the calculation.",
+      "description": "Stores the total number of atoms used in the calculation. For alloys where concentrations of species are given for each site in the unit cell, it stores the number of sites.",
       "dtypeStr": "i",
       "kindStr": "type_dimension",
       "name": "number_of_atoms",