[skip ci] a test

python/tests/composition/test_FormationEnergyCalculator.py

@@ -0,0 +1,31 @@
+import json
+import numpy as np
+import libcasm.xtal as xtal
+from libcasm.composition import (
+    make_standard_origin_and_end_members,
+    CompositionConverter,
+    FormationEnergyCalculator
+)
+
+def test_binary():
+    # read data
+    with open('li_ag_bcc_relax_vasp_data.json', 'r') as f:
+        data = json.load(f)
+    true_formation_energies = np.array([i['formation_energy_per_atom'] for i in data.values()])
+    energies = np.array([i['energy_per_atom'] for i in data.values()])
+    comp = np.array([i['comp'] for i in data.values()]).reshape(1, -1)
+    ref_Ag_energy = -2.717411600000
+    ref_Li_energy = -1.904210800000
+
+    # calculate formation energies
+    end_state_compositions = np.array([[0, 1]]) # Li=0, Li=1
+    end_state_energies = np.array([ref_Ag_energy, ref_Li_energy])
+    formation_energy_calculator = FormationEnergyCalculator(
+        end_state_compositions, end_state_energies
+    )
+    formation_energies = formation_energy_calculator.get_formation_energy(
+        points=comp, energies=energies
+    )
+    assert np.all(np.isclose(formation_energies - true_formation_energies, 0), atol=1e-6)
+
+