Long- and short-range order in the Pd{sub 6}B monoclinic superstructure and M{sub 6}X{sub 5} and M{sub 6}X allied superstructures
Symmetry analysis of the Pd{sub 6}B monoclinic superstructure (space group C2/c) formed in the cubic (with the B1 structure) solid solution of boron in palladium (PdB{sub y}) has been carried out. The formation of this superstructure proceeds as a first-order phase transition via the disorder-order channel including nine nonequivalent superstructure vectors of four stars {l_brace}k{sub 10}{r_brace}, {l_brace}k{sub 4}{r_brace}, {l_brace}k{sub 3}{r_brace}, and {l_brace}k{sub 0}{r_brace}. For the Pd{sub 6}B monoclinic super-structure (space group C2/c), the distribution function for boron atoms is calculated and the interval of admissible values of the long-range order parameters is defined. It is shown that the transition channel determined in this way coincides with the channel in which the M{sub 6}X monoclinic superstructure (space group C2) is formed; therefore, the Pd{sub 6}B superstructure can also be described in space group C2 to the same degree of accuracy. The higher symmetry of the monoclinic model (space group C2/c) suggests that it describes the structure of the Pd{sub 6}B phase (Pd{sub 6}B{open_square}{sub 5}), as well as of mutually inverse phases M{sub 6}X{open_square}{sub 5} and M{sub 6}X{sub 5}{open_square}, more adequately than the model with space group C2. It is shown that superstructures of the M{sub 6}X{open_square}{sub 5} type (space groups C2/c, C2, C2/m, and P3{sub 1}) and inverse superstructures of the M{sub 6}X{sub 5}{open_square} type with the same space groups have the positions of the nearest surrounding of metal atoms by two types of nonmetallic sublattice sites located in the first and second coordination spheres.
- OSTI ID:
- 22028056
- Journal Information:
- Journal of Experimental and Theoretical Physics, Journal Name: Journal of Experimental and Theoretical Physics Journal Issue: 1 Vol. 113; ISSN JTPHES; ISSN 1063-7761
- Country of Publication:
- United States
- Language:
- English
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