Nx1D Hindered Rotor

Compute hindered-rotor-corrected thermochemistry for a molecule by performing geometry optimisation, vibrational analysis, and one-dimensional relaxed dihedral scans for every specified rotor. The partition function is evaluated with the Tamkin Nx1D hindered-rotor treatment using MufiTorsion.

Minimal Example

from atomiverse import (
    LevelOfTheory,
    Nx1DHinderedRotor,
    gf2_xtb,
)


job_builder = Nx1DHinderedRotor(
    atoms=molecule,
    charge=0,
    multiplicity=1,
    level_of_theory=gf2_xtb,
    dihedral_indices=[[0, 1, 2, 3], [1, 2, 3, 4]],
    temperature_start=200.0,
    temperature_stop=800.0,
    temperature_step=50.0,
)
job = job_builder.submit()
result = job.result()

Inputs

Field	Type	Required	Description
atoms	Atoms	Yes	Input geometry (optimised automatically).
charge	int	No	Net charge. Default 0.
multiplicity	int	No	Spin multiplicity. Default 1, minimum 1.
level_of_theory	LevelOfTheory	Yes	QM method for optimisation, vibrations, and scans.
dihedral_indices	list[list[int]]	Yes	One dihedral per rotor. Each inner list holds 4 zero-based atom indices.
scan_step_size	float	No	Step size in degrees for the dihedral scans. Default 15.0.
temperature_start	float	No	First temperature in K. Default 200.0.
temperature_stop	float	No	Last temperature in K. Default 800.0.
temperature_step	float	No	Temperature increment in K. Default 50.0.

Results

Field	Type	Description
zpe_kj_per_mol	float	Zero-point energy in kJ/mol.
external_symmetry_number	int	External rotational symmetry number.
rotor_symmetry_numbers	list[int]	Rotor symmetry numbers (one per rotor).
properties	list[Nx1DHinderedRotorTemperatureProperties]	Per-temperature thermodynamic properties.

Each entry in properties contains:

Field	Type	Description
temperature	float	Temperature in K.
internal_energy_kj_per_mol	float	Internal energy U in kJ/mol.
entropy_j_per_mol_k	float	Entropy S in J/(mol·K).
gibbs_energy_kj_per_mol	float	Gibbs free energy G in kJ/mol.
heat_capacity_j_per_mol_k	float	Heat capacity Cp in J/(mol·K).

Compute Resources

An Nx1D hindered rotor job performs an optimisation, a vibrational analysis, one relaxed 1D dihedral scan per rotor, and a Tamkin Nx1D partition-function evaluation. The walltime multiplier is 240× the base tier walltime. Large molecules (≥ 200 atoms) or many rotors (≥ 15) are assigned higher resource tiers.