Ideal bulk, measuring deviations

The MSD parameters might be characterized as providing a rough measure of the deviation from "ideal" bulk. Of course some problems immediately arise, i.e. ... 

Deviations from bulk-like terminations are quite common in metallic alloys and can involve temperature dependent surface reconstructions, as well as SRO features different from those anticipated in the bulk. First, while the ideal bulklike termination of the LI2(111) surface is the (2x2) structure, according to LEIS, AES and LEED measurements [69] annealing of sputtered Pt3Sn(lll)... 

The second reason for potential deviations between analysis and bulk mass is the inevitable statistical fluctuation of any analytical value. Even in an ideal mixture the characteristic to be determined (e.g. the percentage passing at a particular dimension) will result in different values for each sample. The results of measurements will fluctuate around a mean value whereby results near the mean value are most frequently obtained. There is a probability smaller than unity that a result will be within a certain range around the mean value. Often, the confidence interval for 95% probability is used, which means that 95 out of 100 measurements will produce values within the range. The relative width of this interval depends critically on sample size and the nature of the characteristic to be measured—the larger the sample the narrower the interval. Detailed information is provided in textbooks on statistics and quality control.For example, for the determination of number populations a rule of thumb requires that the sample must consist of at least 1000 or better 10 000 particles. 

Preferential solvation has been studied in the light of various methods, most of which are based on conductance and transference measurements , NMR measurements of the chemical shift of a nucleus in the solute or measurements of the solvatochromism of a solute in the IR or UV-Vis spectral region. Plots of the data obtained from such measurements against the composition of the bulk solvent (usually as a mole fraction) depart clearly from the ideal behavior and the deviation is ascribed to the presence of preferential solvation. 

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