Abstract
An inter-metallic phase in the Al-Mn-Ni system crystallizing in space group Cmcm (No. 63) and refined formula Al61.49Mn11.35Ni4 (called the R' phase) has been synthesized by high-temperature sinter-ing of a mixture with initial chemical composition Al60Mn7Ni3. In comparison with the structure model of the previously reported R phase with composition Al60Mn11Ni4 [Robinson (1954 ▸). Acta Cryst. 7, 494-497], there are two mutually exchanged Mn and Ni sites together with one positionally disordered Al site [occupancy ratio 0.811 (8):0.121 (7)] and one partially occupied Mn site [s.o.f. 0.677 (5)] in the current structure model of the R' phase.
Highlights
An intermetallic phase in the Al–Mn–Ni system crystallizing in space group Cmcm (No 63) and refined formula Al61.49Mn11.35Ni4 has been synthesized by high-temperature sintering of a mixture with initial chemical composition Al60Mn7Ni3
A slightly different crystal-structure model for the R phase in the Al–Mn–Ni system has been refined on basis of single-crystal X-ray diffraction data
The icosahedron centered at Mn3 is surrounded solely by Al atoms (Al3, Al4, Al5, Al6, Al10, Al11, Al12 and Al13) while that centered at Mn4 atom is composed by eleven Al atoms (Al1, Al2, Al4, Al5, Al9, Al11 and Al12) and one Mn atom (Mn4); all of the corresponding atomic sites are fully occupied
Summary
The ternary Al–Mn–Ni alloy system contains a variety of phases with complex or even quasicrystalline structures, most of which are not completely determined. Phase equilibria in the Al-rich region of the Al–Mn–Ni alloy system have been investigated previously In this regard, a ternary phase with composition close to Al60Mn11Ni4 was reported as thermodynamically stable, crystallizing in space group Bbmm (nonconventional setting of space group Cmcm) with unit-cell parameters of a = 23.8, b = 12.5, c = 7.55 A (Raynor, 1944). A slightly different crystal-structure model for the R phase in the Al–Mn–Ni system has been refined on basis of single-crystal X-ray diffraction data. This phase has similar unit-cell parameters to the previously reported R phase (Table 1, using the conventional setting Cmcm).
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