2003/02/06 by Shahrad Amerioun, Sergei I. Simak, S. I. Simak +2 · 82 citations
Chemistry · Engineering · Materials Science · #Alloy #Boron and Carbon Nanomaterials Research #Chemistry #Crystal structure #Crystallography #Intermetallic #Intermetallics and Advanced Alloy Properties #Laves phase #Magnesium Alloys: Properties and Applications #Phase (matter) #Powder diffraction
paper · doi:10.1021/ic020596m
published in Inorganic Chemistry 42(5), 1467-1474 (American Chemical Society)
openalex publication_date 2003/02/06 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/27
Compounds CaAl(2)(-)(x)Mg(x) (0 < or = x < or = 2) were synthesized and structurally characterized by X-ray diffraction experiments. With increasing Mg content x the sequence of Laves phase structures MgCu(2) --> MgNi(2) --> MgZn(2) is revealed. The homogeneity ranges of the underlying phases were determined to be 0 < or = x < 0.24(1) (MgCu(2) type), 0.66(2) < x < 1.07(3) (MgNi(2) type), and 1.51(5) < x < or = 2.0 (MgZn(2) type). Mg/Al site occupancies in CaAl(1.34)Mg(0.66) and in CaAl(0.44)Mg(1.56) were refined from neutron powder diffraction experiments and exposed a pronounced segregation of Al and Mg in MgNi(2)-type CaAl(1.34)Mg(0.66) where Al atoms preferentially occupy the positions corresponding to trigonal bipyramids. In MgZn(2)-type CaAl(0.44)Mg(1.56), however, the Mg/Al distribution was found to be nearly uniform. Structural stability in the quasi-binary system CaAl(2)(-)(x)Mg(x) was investigated by first-principles calculations in which random occupational disorder of Mg and Al was modeled with the virtual crystal approximation. The theoretical calculations reproduced the experimental compositional stability ranges of the three different Laves phase structures very well. Structural changes in the quasi-binary system CaAl(2)(-)(x)Mg(x) are induced by the electron concentration, which decreases with increasing x. The stability of the different Laves phase structures as a function of electron concentration was analyzed by the method of moments.