Line data    Source code

       1             : # SPDX-FileCopyrightText: 2024 PairInteraction Developers
       2             : # SPDX-License-Identifier: LGPL-3.0-or-later
       3             : 
       4             : """Test the pair potential calculation."""
       5             : 
       6           1 : import numpy as np
       7           1 : import pairinteraction.real as pi
       8           1 : import pytest
       9             : 
      10           1 : from .compare_utils import REFERENCE_PATHS, compare_eigensystem_to_reference
      11             : 
      12             : 
      13           1 : def test_pair_potential(generate_reference: bool) -> None:
      14             :     """Test calculating a pair potential."""
      15             :     # Create a single-atom system
      16           1 :     basis = pi.BasisAtom("Rb", n=(58, 62), l=(0, 2))
      17           1 :     print(f"Number of single-atom basis states: {basis.number_of_states}")
      18             : 
      19           1 :     system = pi.SystemAtom(basis)
      20             : 
      21             :     # Create two-atom systems for different interatomic distances
      22           1 :     ket = pi.KetAtom("Rb", n=60, l=0, m=0.5)
      23           1 :     delta_energy = 3  # GHz
      24           1 :     min_energy = 2 * ket.get_energy(unit="GHz") - delta_energy
      25           1 :     max_energy = 2 * ket.get_energy(unit="GHz") + delta_energy
      26             : 
      27           1 :     basis_pair = pi.BasisPair([system, system], energy=(min_energy, max_energy), energy_unit="GHz", m=(1, 1))
      28           1 :     print(f"Number of two-atom basis states: {basis_pair.number_of_states}")
      29             : 
      30           1 :     distances = np.linspace(1, 5, 5)
      31           1 :     system_pairs = [pi.SystemPair(basis_pair).set_distance(d, unit="micrometer") for d in distances]
      32             : 
      33             :     # Diagonalize the systems in parallel
      34           1 :     pi.diagonalize(system_pairs, diagonalizer="eigen", sort_by_energy=True)
      35             : 
      36             :     # Get the overlap with |ket, ket>
      37           1 :     overlaps = np.array([system.get_eigenbasis().get_overlaps([ket, ket]) for system in system_pairs])
      38             : 
      39             :     # Ensure that the overlaps sum up to one
      40           1 :     np.testing.assert_allclose(np.sum(overlaps, axis=1), np.ones(5))
      41             : 
      42             :     # Compare to reference data
      43           1 :     kets = [repr(ket) for ket in basis_pair.kets]
      44           1 :     eigenenergies = np.array([system.get_eigenenergies(unit="GHz") for system in system_pairs])
      45           1 :     eigenvectors = np.array([system.get_eigenbasis().get_coefficients().todense().A1 for system in system_pairs])
      46             : 
      47           1 :     reference_path = REFERENCE_PATHS["pair_potential"]
      48           1 :     if generate_reference:
      49           1 :         reference_path.mkdir(parents=True, exist_ok=True)
      50           1 :         np.savetxt(reference_path / "kets.txt", kets, fmt="%s", delimiter="\t")
      51           1 :         np.savetxt(reference_path / "eigenenergies.txt", eigenenergies)
      52           1 :         np.savetxt(reference_path / "overlaps.txt", overlaps)
      53           1 :         pytest.skip("Reference data generated, skipping comparison test")
      54             : 
      55           1 :     compare_eigensystem_to_reference(reference_path, eigenenergies, overlaps, eigenvectors, kets)