Sodium chloride, crystal structure

FIGURE7.2 A layer ofions in the sodium chloride crystal structure. 

By means of the radius ratio, we have already described the type of local environment around the ions in several types of simple crystals. For example, in the sodium chloride structure (not restricted to NaCl itself), there are six anions surrounding each cation. The sodium chloride crystal structure is shown in Figure 7.4. 

Lead is found as the sulfide, but the other members of the group also form compounds with sulfur. Although PbS has the sodium chloride crystal structure, a silicon sulfide having the formula SiS2 is known that has a chain structure ... 

Spectra of the compounds with sodium chloride crystal structure (Fig. 24) show strong resemblance. Quantitative correlation between lattice parameters and absorption maxima is poor as seen on Table II. 

The ionic hydrides are white solids with high melting points, and all of the alkali metal hydrides have the sodium chloride crystal structure. Because they resemble the salts of the alkali and alkaline earth metals, the ionic hydrides are often referred to as saline or salt-like hydrides. The properties of the alkali metal hydrides are shown in Table 6.3, and those of the alkaline earth hydrides are shown in Table 6.4. 

Consider now the sodium chloride crystal structure shown in Figure 9-40. It is built from sodium ions and chloride ions, and it is kept together by electrostatic forces. The chloride ions are much larger than the sodium ions. As equal numbers of cations and anions build up this structure, the maximum number of neighbors will be the number of the larger chloride ions that can be accommodated around the smaller sodium ion. The opposite would not work although more sodium ions could surround a chloride ion, the same coordination... 

Figure 9-40. The sodium chloride crystal structure in two representations. The space-filling model is from W. Barlow [60],...

Figure 9-56. Part of sodium chloride crystal structure with NaCl, (NaCl)2, and (NaCl)4 units indicated. The species of 3x3x3 ions itself has a high relative abundance in cluster formation.

The Sodium Chloride Crystal Structure. Each atom has six nearest neighbors, with octahedral geometry. This arrangement is known as cubic close packed (ccp). 

Any ionic compound that has the same arrangement of cations and anions as NaCl is said to have the sodium chloride crystal structure. The ionic compounds in this category include AgF, AgCl, AgBr, and the oxides and sulfides of the alkaline earth metals, such as MgO, CaS, etc. The sodium chloride crystal structure is just one of many different possible arrangements of ions in solid ionic compounds. 

Calcium sulfide adopts the sodium chloride crystal structure (Figure P 12.69). How many ions are in the CaS unit cell ... 

In this nonstoichiometric Fe(i t)0 material, conduction is electronic and, in fact, it behaves as a p-type semiconductor—that is, the Fe ions act as electron acceptors, and it is relatively easy to excite an electron from the valence band into an Fe " acceptor state with the formation of a hole. Determine the electrical conductivity of a specimen of wiistite with a hole mobility of 1.0 X 10 m A -s, and for which the value of x is 0.040. Assume that the acceptor states are saturated (i.e., one hole exists for every Fe ion). Wiistite has the sodium chloride crystal structure with a unit cell edge length of 0.437 nm. 

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