Modulation wave form for Na2CO3

Publisher Website
Google Scholar
Abstract
The modulated structure of Na 2CO3 at room temperature, formerly analyzed in the sinusoidal approximation (van Aalst c.s., Acta Cryst. approximation using 3766 non‐zero reflection intensities. These belong to 751 main reflections and 1159, 951, 518, 387 satellites of 1st, 2nd, 3rd, and 4th order respectively. The final R for the weighted set is 9.3%. The average coordinates and the first harmonic components of all modulation functions agree with the former values to within 3σ. The improbable second harmonic variations in the internal distances of the CO3 ion in that former structure are almost eliminated. On the other hand, the large variations in several Na3‐0 distances are now found to approach square‐wave form, indicating a tendency to alternation between two opposite coordinations of Na3. Plots of F0 against fc for each satellite order m show a significant decrease of their ratio with increasing m; for m=4, fo/fc is about 0.8. This effect points to some disorder in the modulation, apart from the normal thermal motion included in the refinement.

This publication has 0 references indexed in Scilit: