kappa3_index#

skfp.descriptors.kappa3_index(mol: Mol) → float#

Third Kappa shape index (K3).

Computes the third kappa shape index [1], which measures molecular shape based on paths of length 3. It is given by the equation:

\[K_3 = \frac{(A + \alpha - 1) (A + \alpha - 3)^2}{P_3^2}\]

where:

  • A is the number of heavy atoms,

  • α is the Hall-Kier alpha index,

  • P3 is the number of paths of length 3.

This index helps characterize the overall shape and structural complexity of molecules.

Parameters:

mol (RDKit Mol object) – The molecule for which the third Kappa shape index is calculated.

References

Examples

>>> from rdkit.Chem import MolFromSmiles
>>> from skfp.descriptors import kappa3_index
>>> mol = MolFromSmiles("C1=CC=CC=C1")  # Benzene
>>> kappa3_index(mol)
0.5823992601400448
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