Inorganic compounds, diffraction

Mighell, eds., Inorganic Compounds Vol. 4, National Bureau of Standards/Joint Committee on Powder Diffraction, Washington, D.C., 1978. 

Technique selection X-ray fluorescence spectroscopy and X-ray diffraction can be used to identify inorganic compounds and their crystal structure. 

Unlike simple inorganic compounds (e.g., NaCl or KC1), polymers do not have a perfectly ordered crystal lattice formation and are not completely crystalline. In fact, they contain both crystalline and amorphous regions. Hence, the X-ray diffractions from them are found to be a mixture of sharp as well as diffused patterns. 

Mark, in the five years he worked at the Institute, established himself as an expert crystallographer. Between 1923 and 1927 more than fifty papers were (co)authored on the lattice structure of metals, simple organic and inorganic compounds, and polymers. The laboratory became known as an efficient, smoothly functioning research organization which attracted all kinds of visitors. Max von Laue was a frequent visitor as was P. P. Ewald, the author of the first book on X-ray diffraction. Others who visited Dahlem were J. R. 

In his x-ray work Mark showed a greater range of interests than the other investigators in the field. Mark and his collaborators studied elements, both metallic and nonmetallic, minerals, inorganic compounds, simple organic compounds, condensed gases, and macromolecular substances, and in addition they studied the physics of x-rays and of the diffraction phenomenon. 

Figure 3 Simulated electron diffraction patterns of an inorganic compound with HOLZ reflections 6° mistilted (left hand side), 3° mistilted (middle) and in correct orientation (right hand side).

A mineral is a naturally occurring, crystalline inorganic compound with a specific chemical composition and crystal structure. Minerals are commonly named to honor a person, to indicate the geographic area where the mineral was discovered, or to highlight some distinctive chemical, crystallographic, or physical characteristic of the substance. Each mineral sample has some obvious properties color, shape, texture, and perhaps odor or taste. However, to determine the precise composition and crystal structure necessary to accurately identify the species, one or several of the following techniques must be employed optical, x-ray diffraction, transmission electron microscopy and diffraction, and chemical and spectral analyses. 

X-Ray Diffraction. X-ray diffraction (XRD) is one of the most common methods to analyze the crystal structure of inorganic compounds. Thus, XRD is used for analysis of metal nanoparticles. 

In a final reference to inorganic compounds it is of interest to note that a neutron diffraction study [9] of Ca(OH)a confirmed the conclusion of Bernal and Meg aw f 10] that this crystal is not hydrogen-bonded. 

File of X-ray powder diffraction standards of the American Society for Testing and Materials. Inorganic Compounds (a) SmN, 30-1104 (b) a-Fe, 6-696. 

By far the most reliable method to determine the absolute configuration of chiral inorganic and organic compounds is by single-crystal X-ray crystallographic analysis.4 By 1974 Saito listed 59 chiral metal complexes whose absolute stmctures were determined by X-ray diffraction.181 Advances in the speed of computer processing and other aspects of X-ray instrumentation have resulted in the ability to determine absolute structures from much smaller crystals. As a consequence, the number of crystal structure determinations of inorganic compounds has increased enormously in recent years. 

The trend in industrial hygiene work is to identify the particular species responsible for an occupational health problem, although assessment of exposures to inorganic materials previously has most often been based on elemental analysis When a solid inorganic compound is to be identified and quantified, X-ray diffraction should be among the approaches considered This paper has outlined the use of X-ray powder diffraction as a tool for the identification and quantitation of crystalline particulates It has been shown that the substrate standard method is the preferred quantitative procedure for several reasons (1) easy adaptability to most analytes (2) fast analysis time (as compared to the internal standard procedure) and (3) accurate determination of matrix absorption effects While there are a number of reasons why a given compound may not be amenable to this technique, it is likely that the list of analytes will be added to in the future ... 

Structure solution in powder diffraction is approached by two different methodologies. One is using the conventional reciprocal space methods. The second is by real space methods where all the known details about the sample (say, molecular details such as bond distances, angles, etc., for an organic molecule, and coordination spheres such as octahedral, tetrahedral etc., in case of inorganic compounds) in question are exploited to solve the structure. 

Crystal Data Determinative Tables. All crystallographic phcises except proteins for which unit cell dimensions have been determined. Vols. 1,3,5,6 Organic and organometallic compounds through 1981. Vols. 2,4 inorganic compounds through 1969. 3rd edn. (Eds., Mighell, A. D., and Stalick, J. K.) U.S. Department of Commerce, NBS/ JCPDS-International Centre for Diffraction Data, Swarthmore, PA (1972-1983). 

Powder Diffraction File Search Manual, Alphabetical Listing and Search Section of Frequently Encountered Phases, Inorganic Compounds. L.G.Berry et.al.(EdsO,Swarthmore, USA, (1976)... 

This chapter presents an overview of the crystal structures of inorganic compounds in which actinide polyhedra are directly coordinated by phosphate or arsenate tetrahedra. Arsenates are considered here for comparative purposes, because of the very similar structural roles played by arsenate and phosphate ions. Structural data are taken mainly from the Inorganic Crystal Stmcture Database [6] and the published literature. Entries from the Powder Dififtaction File of the International Centre for Diffraction Data [7] have been consulted in the case of compounds whose structures may reasonably be inferred. Mixed organic-inorganic compounds [8] and polyoxometalates are not addressed phosphites, phosphinates and arsenites also fall outside the scope of this chapter. Data are tabulated for a given structure type, with phosphates separated... 

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