BaAl4 structure type

EuGa4 (BaAl4 structure type) -with (BaAl43 12AIB2 )2 as code)... 

BaAl4, tllO, structural type and BaA derivative types 7.5.1.3.1 BaAl4, til0, structural type... 

ThCr Si2, tllO structural-type (a BaAl -derivative type) The ThCr2Si2-type structure is one of the ordered ternary variant of the BaAl4 type, frequently found in several ternary compounds. 

AgTlTe2, tI8, structural type (a defect-derivative form of the BaAl4 type)... 

The crystal structure and magnetic behavior of CelrjSij has been characterized by Hiebl et al. (1984). CelrjSij is primitive tetragonal with a BaAl4-derivative type similar to the CaBejGcj-type a = 4.1431(4) and c = 9.8460(50) X-ray powder data of arc-melted alloys subsequently annealed at 1000 °C for 48 h in evacuated silica tubes]. 

The structure types Ce2(Gao.9Geo.i)7 and La2Ali+xGe6 t are the vacancy variant of the orthorhombic SmNiGe3 and can be considered as an intergrowth of AIB2-, deformed Po- and partially vacant BaAl4-type slabs. 

The LuNiSn2 structure can be considered as a plane made up of a combination of the fragments of four structure types - CuAus, AIB2, BaAl4 and a-Po. 

Structure types of antimonides with structures related to BaAl4 type structure... 

In comparison with Al, the systems R-M-Ga are characterized by the greater number of ternary compounds and structure types. Both Al and Ga often show the ThMnjj, BaAl4, Fe2P, Mo2NiB2, etc., structure types. Both elements show prevailing metallic behaviours statistical mixtures of Ga or Al with another metal often occur. 

Fig. 190. Structure type CePt jjGuj 5 as the result of deformation with partial atomic ordering in the BaAl., structure type. The unit-cell connection is shown on the right-hand side (the BaAl4 unit cell is shown by the thin lines, and the CePt gGa, 5 by the heavy ones). Note that on this, and the other figures the R atoms are shown as the largest circles, M as the smallest, and X as the medium ones.

According to Yarmolyuk et al. (YaAGFG, 79) the U3Ni4 i4-type structure together with the 7567 CeNiSij and 7780 CejNi2Sig structures, the last two shown in fig. 31, are members of a structural series of formula R +mT2 M4 ,. The parameter n is the number of ordered AlBj and m the number of ordered BaAl4 structure segments. The structural data for the members of this structural series and their n and m values are listed in table 10. We note that the two end-members of this... 

For a more general discussion of structures which can be considered as an intergrowth of BaAl4 segments and segments of other simple structure types, see 8050 CeNi2Si2. 

The ThCfjSij-type, a BaAl4-type derivative, shown in fig. 50a, is the most frequent structure type found in R-T-B, R-T-Si and R-T-Ge systems. It is also found with phosphides and related compounds. For a recent literature survey see Jeitschko and Jaberg (1980). 

For completeness we should also mention an orthorhombic deformation of the BaAVtype (with unit cell dimensions similar to the BaAl4-type unit cell) found with Ce(Ni, Sb)4 (PePB, 82). No R-T-M compounds with this structure type are known. 

Defect BaAl4 type, extended Hg partial structure [6]... 

In the review by Kanatzidis et al. (2005), the preparation by the tin-flux method is mentioned also for several ternary phosphides and polyphosphides of rare-earth and transition metals. Typically the components (R metal, T metal, P and Sn in an atomic ratio of about 1 4 20 50) in sealed silica tubes were slowly heated, to avoid violent reactions, up to 800°C, annealed at that temperature for 1 week and slowly (2 K/h) cooled to ambient temperature. The tin-rich matrix was dissolved in diluted hydrochloric acid. The authors described the preparation of compounds corresponding for instance to the formula MeT4P12 (Me = heavy rare-earth metals and Th and U, T = Fe, Ru, etc.) and to the series of phases MeT2P2 (Me is a lanthanide or an actinide and T a late transition metal) having a structure related to the BaAl4 or ThCr2Si2 types. 

Figure 7.50. tI10-BaAl4 type structure. Perspective view (a) and projection of a few adjacent cells on the plane x, z (b) (open and filled circles represent atoms withy1 = 0 andy = / ). 

Strukturbericht designation (tI10-BaAl4 type structure) Dl3. 

The crystal chemistry of the phosphide oxides discussed above is closely related to the structural slabs of the well-known BaZn2P2 type (isolated P ) /BaAl4 type (P2 pairs) and related compounds. This is different for the phosphide halide structures. Some relevant structures of the phosphide halides are presented in Figure 21 and a list is given in Table 9. These structures contain isolated phosphorus atoms, P2 pairs, or one-dimensional spirals like in the structure of elemental selenium. 

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