Abstract
Here, structural parameters of various structure reports on RSi2 and R2TSi3 compounds [where R is an alkaline earth metal, a rare earth metal (i.e. an element of the Sc group or a lathanide), or an actinide and T is a transition metal] are summarized. The parameters comprising composition, lattice parameters a and c, ratio c/a, formula unit per unit cell and structure type are tabulated. The relationships between the underlying structure types are presented within a group-subgroup scheme (Bärnighausen diagram). Additionally, unexpectedly missing compounds within the R2TSi3 compounds were examined with density functional theory and compounds that are promising candidates for synthesis are listed. Furthermore, a correlation was detected between the orthorhombic AlB2-like lattices of, for example, Ca2AgSi3 and the divalence of R and the monovalence of T. Finally, a potential tetragonal structure with ordered Si/T sites is proposed.
Highlights
As it has been widely discussed in the literature (Hoffmann & Pottgen, 2001; Pan et al, 2013; Peter & Kanatzidis, 2012), the RSi2 and R2TSi3 compounds crystallize with the hexagonal AlB2 and the tetragonal ThSi2 type and derivative structure types (Hoffmann & Pottgen, 2001)
The vast majority of compounds were reported to form superstructures which, in general, allow only slight variations in stoichiometry. We discuss those structures as distinct phases due to the changes in symmetry at these particular compositions in the phase diagrams
We present an extensive literature study of the RSi2 and R2TSi3 compounds crystallizing in AlB2- and ThSi2-like structures complemented by density functional theory (DFT) calculations
Summary
The rare earth disilicides RSi2 have been the subject of numerous studies in the past few decades mainly due to their exciting magnetic properties, such as magnetic ordering phenomena (Wang et al, 2019; Pan et al, 2013; Kotsanidis et al, 1990; Li et al, 1998a, 2002a, 2013; Bazela et al, 2003; Inosov et al, 2009), especially ferromagnetic ordering (Majumdar et al, 1998, 1999b; Li et al, 1999, 2002a,b, 2003, 2013; Frontzek et al, 2004), their spin-glass-like behavior (Li et al, 1998a, 1999, 2002b, 2003; Kimura et al, 1999; Szytuła et al, 1999, 2000; Paulose et al, 2003; Lu et al, 2013) and Ruderman– Kittel–Kasuya–Yosida (RKKY) interactions (Li et al, 2002b; Inosov et al, 2009; Tang et al, 2010a,b; Lu et al, 2013), which have been studied since the early 1980s. This reflects in the obsolete structuretype names -USi2 and -ThSi2 for tetragonal ThSi2 as well as -USi2 and -ThSi2 for hexagonal AlB2 (Evers et al, 1980; Yashima et al, 1982a,b,c; Yashima & Satoh, 1982; Lejay et al, 1983; Evers et al, 1983; Weigel et al, 1984; Sato et al, 1984; Zhong et al, 1985; Chevalier et al, 1986; Dhar et al, 1987)
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