Table 4.
Best fits for the Fe K-edge EXAFS data of isolated precursor over the k-range of 2–16 Å−1.
| Isolated Precursor (from NifEN) | |||
|---|---|---|---|
| Scatterer | N | R (Å) | σ (Å2) |
| Fe-X | 0.7 | 1.99 | 0.0039 |
| Fe-S | 3.0 | 2.26 | 0.0038 |
| Fe-Fe short | 3.3 | 2.65 | 0.0046 |
| Fe-Fe short | 0.5 | 2.85 | 0.0074 |
| Fe-Fe long | 1.5 | 3.71 | 0.0046 |
| ΔE0 (eV) | −10.8 | ||
| Weighted F | 0.141 | ||
Coordination number (N), interatomic distance (R, Å), mean-square thermal and static disorder in distance (σ2, Å2), and EXAFS threshold energy adjustment from 7130 eV (ΔE0, eV) were varied in the fits. Estimated errors are ±0.02 Å in R, ±0.0001 Å2 in σ2, and ±20% in N. The goodness of fit, F, is defined as F = [Σk6(χexper.− χcalc.)2/Σk6(χexper.)2]0.5. The Fe-X distance was calculated by assuming X as N, although indistinguishable results could be obtained by assuming X as C or O.