Check multiplicity argument passed to compilation script for HF numeric. (#24)

* Catch incorrect multiplicities passed when compiling numeric dataset.

Use the table of multiplicities for the isoelectronic series to verify
the mult parameter in the run scripts. The results from HF numeric
calculations are only for the most stable electronic configuration
of an atomic species.

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Author: gabrielasd

atomdb/datasets/numeric/__init__.py

@@ -31,6 +31,8 @@
 
 import atomdb
 
+from atomdb.api import MULTIPLICITIES
+
 
 def load_numerical_hf_data():
     """Load data from desnity.out file into a `SpeciesTable`."""
@@ -107,7 +109,10 @@ def run(elem, charge, mult, nexc, dataset, datapath):
     # Check arguments
     if nexc != 0:
         raise ValueError("Nonzero value of `nexc` is not currently supported")
-    # FIXME: check input multiplicity against tabulated values for isoelectronic serie
+    if charge < -1:
+        raise ValueError("The charge must be greater than or equal to -1.")
+    if charge == elem:
+        raise ValueError("The atomic number and charge cannot be the same.")
 
     # Set up internal variables
     elem = atomdb.element_symbol(elem)
@@ -118,6 +123,11 @@ def run(elem, charge, mult, nexc, dataset, datapath):
     n_dn = (nelec - nspin) // 2
     basis = None
 
+    # Check that the input multiplicity corresponds to the most stable electronic configuration.
+    # For charged species take the multiplicity from the neutral isoelectronic species.
+    if mult != MULTIPLICITIES[nelec]:
+        raise ValueError(f"Multiplicity {mult} not available for {elem} with charge = {charge}.")
+
     species_table = load_numerical_hf_data()
     data = species_table[(natom, nelec)]