NaCI-type

Fig. 2.9 S implified interaction scheme of ir with X in the solid, (a) Hypothetical TIP in the NaCI type of structure,...

Fig. 8.2 S implified structures of CaC2 l-lll (from (a) to (c)), displayed as derivatives of the NaCI type structure, neglecting the relation of their true crystallographic unit cells.

Figure 10.3 Carbide hardnesses vs. characteristic vibrational energy densities derived from average force constants (entropic specific heat). After Grimvall and Theissen (1986). The crystal structures are of the NaCi type. The hardness data are fromTeter (1998).

Table IX. M-S Distances Observed and Calculated in NaCI-Type Solid Solutions...

Looking at the trends in atomic properties, we can see that K atom is bigger than Ca and consequently that Ca is smaller than K but bigger than Ca. Thus, the ionic radius for Ca can be approximated as in between that of K and Ca. Since KCl has an NaCI-type structure, we can safely assume that CaCl would have the same, so we are using cationic radii for coordination six (138 + 100)pm/2 = 119 pm. We have ... 

Cesium chloride CsCl Cubic (CsCI type) (s), d = 3.64 Cubic (NaCI type) (m), d = 3.64... 

The space group of GeTe is a subgroup common to the two branches of the family tree. The structure can be obtained from the NaCI type by introducing a small asymmetry in the distance between alternating layers of Na and Cl atoms. Alternatively, the structure can be derived from a-As by an ordered substitution of As by Ge and Te in the layers parallel to the trigonal axis. 

NaCI-type compound ScS YS LuS YTe LuSe LaS LaSe LaTe... 

Fig. 33.2. Room-temperature lattice constants of NaCI-type pnictides versus cation radii (ionic radii given by Shannon, 1976).

J is the exchange parameter for the nth neighbors) for NaCI-type compounds. 

Checking the frequency of occurrence of the B1 (NaCI)-type structure among the 1 1 compounds of the metals (Manes and Benedict 1985) shows that at ambient pressure and temperature practically all LnX and AnX compounds have this structure, while only f of the other MX compounds (M metal) crystallize in this structure type. This may indicate that either the incomplete f shells or the low d-electron counts favor the formation of the Bl-type structure. 

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