BaAl4 structure

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

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... 

In the BaAl4 structure with crystal-chemical formula BaAl + Al there are two crystallographically different Al sites, i.e., four tetrahedral sites and four antiprismatic sites per tetragonal unit cell. In the BaAVtype derivatives the Al... 

Many ternary borides crystallize with the ordered BaAl4 or ThCr2Si2 structure ... 

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. 

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

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. 

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 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. 

For the structures of the series BaAl4 - AIB2 equation (1) can be written as follows ... 

The same space groups are possible for the Intergrowth structures of the series BaAl4 - YlrQe2. The only one representative of this series Is Y3Pt4Gee (numeric code which was found by Venturini Malaman (1990). 

Figure 5. The structures of the linear inhomogeneous series BaAi - CaF (1 - 4) and BaAl4 - Cap2 - Cu (5) together wirii the parent stmcture BaAl and the location of die corresponding ternary compounds in the ternary stem Ce-Ni- Ga.

Venturini, G. Malaman, B. (1990). Crystal structure of YgPtjGeg an intergrowth of BaAl4 and YlrGe2 slabs. J. Less-Common Met 167,45-52. 

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 crystal structure of ErPtjSij has been refined from X-ray powder diffraction data BaAl4-type of structure, I4/mrnm, a = 4.115, c = 9.822 and — 12.25 kg/dm. Pt and Si atoms were claimed to occupy the 4d and 4e sites in a random distribution, R = 0.156. The z-parameter has been evaluated as r(4e)= 0.370 (Mayer and Yetor, 1977). For sample preparation, see LaPtjSij. At variance Ballestracci and Astier (1978) observed ErPtjSij with a primitive tetragonal unit cell and reported a = 4.124 and c = 9.82 (X-ray powder diffraction of alloys melted in an induction furnace under argon). The lower crystal symmetry with an atomic arrangement similar to the CaBejGej-type was confirmed by Rogl (1984) from X-ray powder data of arc-melted alloys a = 4.1304(4), c = 9.8633(42) CePtjSij-type. 

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. 

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