def run_ideal_gas(
atoms: Atoms,
vib_freqs: list[float | complex],
energy: float = 0.0,
spin_multiplicity: int | None = None,
) -> IdealGasThermo:
"""
Create an IdealGasThermo object for a molecule from a given vibrational analysis.
This is for free gases only and will not be valid for solids or adsorbates on
surfaces. Any imaginary vibrational modes after the 3N-5/3N-6 cut will simply be
ignored.
Parameters
----------
atoms
The Atoms object associated with the vibrational analysis.
vib_freqs
The list of vibrations to use in cm^-1, typically obtained from
Vibrations.get_frequencies().
energy
Potential energy in eV. If 0 eV, then the thermochemical correction is
computed.
spin_multiplicity
The spin multiplicity (2S+1). If None, this will be determined
automatically from the attached magnetic moments.
Returns
-------
IdealGasThermo object
"""
# Ensure all negative modes are made complex
for i, f in enumerate(vib_freqs):
if not isinstance(f, complex) and f < 0:
vib_freqs[i] = complex(0 - f * 1j)
# Convert vibrational frequencies to energies
vib_energies = [f * units.invcm for f in vib_freqs]
# Get the spin from the Atoms object.
if spin_multiplicity:
spin = (spin_multiplicity - 1) / 2
elif (
getattr(atoms, "calc", None) is not None
and getattr(atoms.calc, "results", None) is not None
and atoms.calc.results.get("magmom", None) is not None
):
spin = round(atoms.calc.results["magmom"]) / 2
elif (
getattr(atoms, "calc", None) is not None
and getattr(atoms.calc, "results", None) is not None
and atoms.calc.results.get("magmoms", None) is not None
):
spin = round(np.sum(atoms.calc.results["magmoms"])) / 2
elif atoms.has("initial_magmoms"):
spin = round(np.sum(atoms.get_initial_magnetic_moments())) / 2
else:
spin = 0
# Get symmetry for later use
natoms = len(atoms)
mol = AseAtomsAdaptor().get_molecule(atoms, charge_spin_check=False)
point_group_data = PointGroupData().from_molecule(mol)
# Get the geometry
if natoms == 1:
geometry = "monatomic"
elif point_group_data.linear:
geometry = "linear"
else:
geometry = "nonlinear"
return IdealGasThermo(
vib_energies,
geometry,
potentialenergy=energy,
atoms=atoms,
symmetrynumber=point_group_data.rotation_number,
spin=spin,
ignore_imag_modes=True,
)