Crystal Field Stabilization Energy
Definition and meaning of Crystal Field Stabilization Energy in chemistry.
Crystal field stabilization energy (CFSE) is the net lowering in energy that a transition-metal ion's d electrons experience when they occupy the split d orbitals produced by a surrounding ligand field, compared with a hypothetical spherically symmetric field of the same total charge.
In more detail
In an octahedral field, the five d orbitals split into a lower-energy t2g set (dxy, dxz, dyz) and a higher-energy eg set (dz2, dx2−y2), separated by the splitting energy Δo. Each electron in t2g lowers the energy by 0.4Δo, while each electron in eg raises it by 0.6Δo; summing these contributions (and any extra electron-pairing energy for low-spin cases) gives the CFSE. CFSE helps explain periodic trends in hydration enthalpies, lattice energies, ionic radii, and why some d-electron counts favor high-spin versus low-spin arrangements.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Octahedral formula | CFSE = (−0.4·n(t2g) + 0.6·n(eg))Δo |
| Splitting energy unit | Δo = 10Dq |
| Tetrahedral splitting | Δt ≈ (4/9)Δo |
For the d1 ion in [Ti(H2O)6]3+, the single d electron occupies a t2g orbital, giving CFSE = −0.4Δo (equivalently −4Dq, since Δo = 10Dq).
Frequently asked questions
Why do d0, high-spin d5, and d10 configurations have zero CFSE?
Because their electrons are spread evenly across all five d orbitals (empty, singly occupied throughout, or completely filled), so there is no net energetic preference for the t2g set over the eg set.
How does CFSE determine high-spin versus low-spin complexes?
When Δo is larger than the electron-pairing energy P, electrons fill t2g and pair up before entering eg, maximizing CFSE (low-spin); when Δo is smaller than P, electrons occupy eg singly first, sacrificing some CFSE to avoid the pairing energy cost (high-spin).