ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
The crystal structure of α-silicon nitride (Si3N4) was refined by the Rietveld method using synchrotron radiation powder diffraction data (wavelength = 1.2 Å) collected at station BL-4B2 in the Photon Factory. A refinement procedure that adopted a new weight function, w = 1/Y_o^e (Yo is the observed profile intensity and e ∼ 2), for the least-squares fitting [Toraya (1998). J. Appl. Cryst. 31, 333–343] was studied. The most reasonable structural parameters were obtained with e = 1.7. Crystal data of α-Si3N4: trigonal, P31c, a = 7.75193 (3), c = 5.61949 (4) Å, V = 292.447 (3) Å3, Z = 4; Rp = 5.08, Rwp = 6.50, RB = 3.36, RF = 2.26%. The following five factors are considered equally important for deriving accurate structural parameters from powder diffraction data: (i) sufficiently large sin θ/λ range of 〉0.8 Å−1; (ii) adequate counting statistics; (iii) correct profile model; (iv) proper weighting on observations to give a uniform distribution of the mean weighted squared residuals; (v) high-angular-resolution powder diffraction data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889899013060
