Crystal structure parameters

Measures surface crystal structure parameters, sensitive to structural defects... 

In attempts to verify the crystal chemistry of Fe3+ ions in these minerals, other correlations have been sought between the two Mossbauer spectral parameters, I.S. or Q.S., and crystal structure parameters based on bond distances and site distortion properties (2,5-9). These correlations are now critically examined. 

Correlations..Between.Isomer Shift.and.Crystal Structure Parameters... 

Quadrupole Splitting Versus Crystal Structure Parameters. 

Fig. 32. Peak shapes, calculated from crystal structure parameters for the heptamo-lybdate ion, Mo70246", and for two octamolybdates Mo80264 and Mo80288". The separate contributions from Mo—Mo distances (short dashes), Mo—0 distances (dotted lines), and O—0 distances (long dashes) are shown.

TABLE lO-I Some Crystal Structure Parameters of Amides and Peptides... 

Calcite can easily be identified without a microscope by its ready dissolution in I N HCl, often fizzing or forming bubbles indicating the liberation of CO2. The other isostructural members of the calcite group are less soluble, but since all of these minerals are usually well crystallized. X-ray diffraction and analysis can identify them as a group member. In addition, the diffraction maxima positions can be used to estimate the quantities of different elements incorporated. The diffraction analysis relies on a physical shift in the crystal structure parameters based on the size of the cation, and is not a chemical analysis. 

Hill, R. J., and Madsen, I. C. The effect of profile step width on the determination of crystal structure parameters and estimated standard deviations by X-ray Rietveld analysis. J. Appl. Cryst. 19, 10-18 (1986). 

Correlation between parameters A correlation is a measure of the extent to which two mathematical variables are dependent on each other. In the least-squares refinement of a crystal structure, parameters related by symmetry are completely correlated, and temperature factors and occupancy factors are often highly correlated. 

Table 2 Crystal structure parameters of cyclo-S (standard deviations in parentheses). There are three (one) molecules per unit (primitive) cell ...

Table 3 Crystal structure parameters brackets) [20, 71] of y-Sy and S-Sy at 163 K (standard deviations in...

Table 20 Crystal structure parameters of 2nd fibrous suUur (S -=Sa,i) and of laminar sulfur (S j=Sa,2) [54, 115]. The molecular parameters were claimed to be very similar to those of fibrous sulfur, ...

Table 8-1. Comparison of simulated and experimental crystal structure parameters for pyrophyllite (all distances in nm).

Curves 7, for Pt and for Ir, show a different intrinsic activity but have the same shape. Barbier and Marecot (267) have suggested that since Pt and Ir have almost identical crystal structural parameters, the similarity in the curves 7 must mean that the structure sensitivity arises from geometric factors. The monotonic nature and the direction of the variation support this explanation also. 

Table V-12 [54GUL/AND], Crystal structure parameters for zirconium hydride compounds...

Table V-26 Stoichiometries and crystal structure parameters for zirconium sulphide compounds [57HAH/HAR]...

Crystal structure parameters for zirconium hydride compounds... 

Stoichiometries and crystal structure parameters for zirconium sulphide... 

The most artificial aspect of this model, which is expressed in Eq. 3.55, is the monolayer approximation, and in fact it is unnecessary to require all layers below the top monolayer to have the bulk composition. Williams and Nason [25] presented a four-layer model in which the top four layers were allowed to have compositions different from the bulk, while the fifth and deeper layers had the bulk composition. The results of the derivation are four coupled equations relating the surface composition of the four layers to T, Q, and the crystal-structure parameters. 

Crystal structure parameters have been obtained for MCl (M = Th, Pa, U, or Np) and MBr (M = Th or Pa) by a comparison of quantitative X-ray powder data with single crystal studies. Bond lengths for the halides were calculated, and the covalent radii of the ions estimated at 1.71 (Th), 1.64 (Pa), and 1.61 A (U and Np), respectively. CfF3 exhibited a high-temperature... 

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