Extending support for larger atomic numbers

doc/releases/changelog-dev.md

@@ -77,6 +77,9 @@
 * The qchem module has dedicated functions for calling `pyscf` and `openfermion` backends.
  [(#5553)](https://github.com/PennyLaneAI/pennylane/pull/5553)
 
+* Molecules and Hamiltonians can be constructed for elements present in the periodic table.
+ [(#5821)](https://github.com/PennyLaneAI/pennylane/pull/5821)
+
 <h4>Mid-circuit measurements and dynamic circuits</h4>
 
 * Rationalize MCM tests, removing most end-to-end tests from the native MCM test file,
@@ -359,6 +362,7 @@
 This release contains contributions from (in alphabetical order):
 
 Guillermo Alonso-Linaje,
+Utkarsh Azad
 Lillian M. A. Frederiksen,
 Gabriel Bottrill,
 Astral Cai,

pennylane/qchem/basis_data.py

@@ -20,18 +20,28 @@
 
 import itertools
 
+# fmt: off
 atomic_numbers = {
- "H": 1,
- "He": 2,
- "Li": 3,
- "Be": 4,
- "B": 5,
- "C": 6,
- "N": 7,
- "O": 8,
- "F": 9,
- "Ne": 10,
+ 'H': 1, 'He': 2, # Period 1
+ 'Li': 3, 'Be': 4, 'B': 5, 'C': 6, 'N': 7, 'O': 8, 'F': 9, 'Ne': 10, # Period 2
+ 'Na': 11, 'Mg': 12, 'Al': 13, 'Si': 14, 'P': 15, 'S': 16, 'Cl': 17, 'Ar': 18, # Period 3
+ 'K': 19, 'Ca': 20, 'Sc': 21, 'Ti': 22, 'V': 23, 'Cr': 24, 'Mn': 25, 'Fe': 26, 'Co': 27, # Period 4
+ 'Ni': 28, 'Cu': 29, 'Zn': 30, 'Ga': 31, 'Ge': 32, 'As': 33, 'Se': 34, 'Br': 35, 'Kr': 36,
+ 'Rb': 37, 'Sr': 38, 'Y': 39, 'Zr': 40, 'Nb': 41, 'Mo': 42, 'Tc': 43, 'Ru': 44, 'Rh': 45, # Period 5
+ 'Pd': 46, 'Ag': 47, 'Cd': 48, 'In': 49, 'Sn': 50, 'Sb': 51, 'Te': 52, 'I': 53, 'Xe': 54,
+ 'Cs': 55, 'Ba': 56, # Period 6
+ 'La': 57, 'Ce': 58, 'Pr': 59, 'Nd': 60, 'Pm': 61, 'Sm': 62, 'Eu': 63, 'Gd': 64, 'Tb': 65, # Lanthanides
+ 'Dy': 66, 'Ho': 67, 'Er': 68, 'Tm': 69, 'Yb': 70, 'Lu': 71,
+ 'Hf': 72, 'Ta': 73, 'W': 74, 'Re': 75, 'Os': 76, 'Ir': 77, 'Pt': 78, 'Au': 79, 'Hg': 80, # Period 6
+ 'Tl': 81, 'Pb': 82, 'Bi': 83, 'Po': 84, 'At': 85, 'Rn': 86,
+ 'Fr': 87, 'Ra': 88, # Period 7
+ 'Ac': 89, 'Th': 90, 'Pa': 91, 'U': 92, 'Np': 93, 'Pu': 94, 'Am': 95, 'Cm': 96, 'Bk': 97, # Actinides
+ 'Cf': 98, 'Es': 99, 'Fm': 100, 'Md': 101, 'No': 102, 'Lr': 103,
+ 'Rf': 104, 'Db': 105, 'Sg': 106, 'Bh': 107, 'Hs': 108, 'Mt': 109, 'Ds': 110, 'Rg': 111, # Period 7
+ 'Cn': 112, 'Nh': 113, 'Fl': 114, 'Mc': 115, 'Lv': 116, 'Ts': 117, 'Og': 118
 }
+# fmt: on
+
 
 STO3G = {
  "H": {
@@ -797,11 +807,14 @@ def load_basisset(basis, element):
  "[3]": "F",
  "[4]": "G",
  "[5]": "H",
+ "[6]": "I",
  }
 
- element = str(atomic_numbers[element])
+ atomic_number = atomic_numbers.get(element, None)
+ if atomic_number is None:
+ raise ValueError(f"Requested element {element} doesn't exist in the periodic table.")
 
- data = bse.get_basis(basis)["elements"][element]["electron_shells"]
+ data = bse.get_basis(basis)["elements"][str(atomic_number)]["electron_shells"]
 
  orbitals = []
  exponents = []

pennylane/qchem/basis_set.py

@@ -100,6 +100,15 @@ def atom_basis_data(name, atom, load_data=False):
  if load_data:
  basis = load_basisset(name, atom)
  else:
+ basis = basis_sets[name].get(atom, None)
+ if basis is None:
+ raise ValueError(
+ "Currently, internally supported basis sets: 'sto-3g', '6-31g', '6-311g' and "
+ "'cc-pvdz', support only first- or second-row elements of the periodic table. "
+ "Please consider using `load_data=True` to download an extended version of "
+ f"{basis_sets[name]} from an external library that can be installed with: "
+ "pip install basis-set-exchange."
+ )
  basis = basis_sets[name][atom]
 
  params = []

pennylane/qchem/openfermion_pyscf.py

@@ -609,10 +609,7 @@ def dipole_of(
 
  for i in symbols:
  if i not in atomic_numbers:
- raise ValueError(
- f"Currently, only first- or second-row elements of the periodic table are supported;"
- f" got element {i}"
- )
+ raise ValueError(f"Requested element {i} doesn't exist in the periodic table")
 
  hf_file = qml.qchem.meanfield(symbols, coordinates, name, charge, mult, basis, package, outpath)
 

tests/qchem/of_tests/test_dipole_of.py

@@ -273,7 +273,7 @@ def circuit(hf_state, obs):
  ("symbols", "coords", "mult", "msg_match"),
  [
  (["H", "H"], x_h2, 2, "this functionality is constrained to Hartree-Fock states"),
- (["H", "Ca"], x_h2, 1, "only first- or second-row elements of the periodic table"),
+ (["H", "Cx"], x_h2, 1, "Requested element Cx doesn't exist in the periodic table"),
  ],
 )
 @pytest.mark.usefixtures("skip_if_no_openfermion_support")

tests/qchem/test_basis_set.py

@@ -477,6 +477,15 @@ def test_mol_basis_data(self, basis_data):
 
  assert np.allclose(params, params_ref)
 
+ def test_mol_basis_data_error(self):
+ """Test that correct error is raised if the element is not present in the internal basis-sets"""
+
+ with pytest.raises(ValueError, match="Currently, internally supported basis sets"):
+ qchem.basis_set.atom_basis_data(name="sto-3g", atom="Os")
+
+ with pytest.raises(ValueError, match="doesn't exist in the periodic table"):
+ qchem.basis_data.load_basisset(basis="sto-3g", element="Ox")
+
 
 class TestLoadBasis:
  """Tests for loading data from external libraries."""

tests/qchem/test_molecule.py

@@ -49,7 +49,7 @@ def test_basis_error(self, symbols, geometry):
  @pytest.mark.parametrize(
  ("symbols", "geometry"),
  [
- (["H", "Og"], np.array([[0.0, 0.0, 0.0], [0.0, 0.0, 1.0]])),
+ (["H", "Ox"], np.array([[0.0, 0.0, 0.0], [0.0, 0.0, 1.0]])),
  ],
  )
  def test_symbol_error(self, symbols, geometry):