Merge pull request #177 from singularitti:singularitti/issue176

Fix wyckoffs in dataset

src/core.jl

@@ -16,6 +16,7 @@ export Lattice,
     atomtypes
 
 const basis_vectors = basisvectors  # For backward compatibility
+const WYCKOFF_LETTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"  # See https://github.com/spglib/spglib/blob/v2.2.0/python/spglib/spglib.py#L364
 
 """
     SpglibCell(lattice, positions, atoms, magmoms=[])
@@ -349,7 +350,7 @@ function Dataset(dataset::SpglibDataset)
         unsafe_load(dataset.translations, i) for i in Base.OneTo(dataset.n_operations)
     )
     wyckoffs = unsafe_wrap(Vector{Int32}, dataset.wyckoffs, dataset.n_atoms)
-    wyckoffs = [('a':'z')[w + 1] for w in wyckoffs]  # Need to add 1 because of C-index starts from 0
+    wyckoffs = [WYCKOFF_LETTERS[w + 1] for w in wyckoffs]  # Need to add 1 because of C-index starts from 0
     site_symmetry_symbols = tostring.(
         unsafe_load(dataset.site_symmetry_symbols, i) for i in Base.OneTo(dataset.n_atoms)
     )

test/symmetry.jl

@@ -1543,3 +1543,23 @@ end
     @test get_dataset_with_hall_number(cell, dataset.hall_number) == dataset
     @test get_schoenflies(cell, 1e-5) == "C6v^4"
 end
+
+@testset "Test issue 176" begin  # See https://github.com/singularitti/Spglib.jl/issues/176
+    lattice = [6.42 0 0; 0.0 6.41 0; 0.0 0.0 6.44]
+    x = 0.79
+    y = 1 - x
+    positions = [
+        [y, y, x],
+        [y, x, y],
+        [x, y, y],
+        [x, x, x],
+        [x, x, y],
+        [x, y, x],
+        [y, x, x],
+        [y, y, y],
+    ]
+    atoms = ["Ga", "Ga", "Ga", "Ga", "Ga", "Ga", "Ga", "Ga"]
+    cell = Cell(lattice, positions, atoms)
+    dataset = get_dataset(cell)
+    @test dataset.wyckoffs == ['A', 'A', 'A', 'A', 'A', 'A', 'A', 'A']  # Compared with Python results
+end