CsCl superstructures

See also Fig. 3.8. where the nearest-neighbour number (NNN) of the two atomic species is evidently eight. A list and the histogram of the atomic distances with the corresponding number of the equidistant neighbours are shown in Fig. 3.17. The resulting CNE is 14. In Fig. 3.31 the derivative CsCl superstructure MnCu2Al type... 

Ternary indides with CsCl superstructures or Heusler phases... 

Magnetic properties of rare earth metal-transition metal-indides with CsCl superstructures or Heusler type structure... 

Superstructure of the CsCl type with eightfold unit cell. Left, lower half and right, upper half of the cell in projection onto the plane of the paper, a, b, c, and d designate four different kinds of atomic sites that can be occupied in the following ways ... 

The term Laves phases is used for certain alloys with the composition MM3, the M atoms being bigger than the M atoms. The classical representative is MgCu2 its structure is shown in Fig. 15.4. It can be regarded as a superstructure of the CsCl type as in Fig. 15.3, with the following occupation of the positions a, b, c, and d ... 

Body-centered cubic sphere packing => CsCl type => superstructures of the CsCl type... 

An example where, due to ordering, we observe perhaps in a more immediate way, the increase of the unit cell size (formation of a multiple cell) is the MnCu2Al-type structure (representative of the so-called Heusler alloys) which can be considered a derivative structure (superstructure) of the cP2-CsCl type, which in turn is a superstructure of the W-type structure, corresponding to a non-primitive cubic cI2... 

The W body-centred cubic structure can be compared with the simple cubic CsCl-type structure (which can be obtained from the W type by an ordered substitution of the atoms) and with the MnCu2Al-type structure ( ordered superstructure of the CsCl type) see Fig. 3.31 and notice the typical eight (cubic) coordination. 

L.a Cr,j Nj, crystallizes with a superstructure of rocksalt and is a superconductor below 2.7 K [262], The partial occupancy of the nitrogen positions was fixed at the experimental stoichiometry. LaA NT formed at high pressure reportedly has a structure similar to CsCl [263]. La(NH,)3 is formed under ammonia at 400 MPa and crystallizes with amide groups in approximate cubic eutaxy [264]. 

Of prime importance is the possibility to form superstructures with a twofold or even threefold transformation length by combining 8 or even 27 cells of CsCl type. In such systems different atoms can occupy the central position of each individual body centered cubic unit, providing a great variety of structures. The different lattice positions for a stack of 8 CsCl units are shown in Figure 2.6. 

Figure 2.6 Different lattice positions in a superstructure of 8 CsCl units. (A) Lower half of unit ceU and (B) upper half of unit cell.

The YPdjSn structure with MnCu2Al (Heusler phase)-type is shown in fig. 42. This face-centred structure is a superstructure of the CsCl-type. 

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