Moved pymatgen imports.

tests/test_ewaldsummatrix.py

@@ -209,7 +209,7 @@ def test_electrostatics(setup):
 
     # The value in each matrix element should correspond to the Coulomb
     # energy of a system with with only those atoms. Here the energies from
-    # the Ewald matrix are compared against the Ewald energy calculated
+    # the Ewald matrix are compared against the Ewald energy precalculated
     # with pymatgen.
     energy_pymatgen = load_ewald(create_args)
     assert np.allclose(energy_matrix, energy_pymatgen, atol=1e-5, rtol=0)

tests/testutils.py

@@ -5,8 +5,6 @@
 from scipy.linalg import sqrtm
 from ase import Atoms
 
-# from pymatgen.analysis.ewald import EwaldSummation
-# from pymatgen.core.structure import Structure
 from dscribe.descriptors import SOAP
 from joblib import Parallel, delayed
 from conftest import get_simple_finite
@@ -404,6 +402,9 @@ def save_poly_coefficients():
 
 def calculate_ewald(system, a=None, r_cut=None, g_cut=None, accuracy=None):
     """Used to precalculate the Ewald summation results using pymatgen."""
+    from pymatgen.analysis.ewald import EwaldSummation
+    from pymatgen.core.structure import Structure
+
     positions = system.get_positions()
     atomic_num = system.get_atomic_numbers()
     n_atoms = len(system)