CaTMg₂ and CaTCd₂ (T =Rh, Pd, Pt) with YPd₂Si-type Structure

Abstract

The intermetallic calcium compounds CaT Mg 2 and CaT Cd 2 (T = Rh, Pd, Pt) were obtained by high-frequency melting of the elements in sealed niobium ampoules or through reactions in muffle furnaces. The polycrystalline samples were characterized by powder X-ray diffraction. They crystallize with a site occupancy variant of YPd 2 Si, a ternary ordered version of

Magnesium and Cadmium in Covalently‐Bonded Lonsdaleite Networks: Synthesis, Structure, and Bonding of AETMg2 and SrTCd2 (AE = Ca, Sr; T = Pd, Ag, Pt, Au)

“…This is confirmed from the larger iCOOP(Pd–Mg) vs. iCOOP(Pd–Sr) areas below the lines. This is similar to CaPdMg 2 43. Different features appear for the COOP and iCOOP in the cadmium compound with weakly bonding Pd–Sr and low lying Pd–Cd bonding interactions but largely antibonding Pd–Cd below the Pd PDOS energy position (Figure 2).…”

“…However, the stability range of such compounds is not solely determined by electronic reasons. CaPdCd 2 , CaPtCd 2 , CaPdMg 2 , and CaPtMg 2 43 also have VEC = 16, but they crystallize with the YSiPd 2 type structure,18 a ternary ordered version of the cementite structure, Fe 3 C 19. These phases will be communicated in a forthcoming contribution.…”

Ca2Pd2Cd with W2B2Co-type Structure

“…Currently we systematically investigate the AE-T -Cd systems with respect to phase formation and crystal chemistry. First results show close similarities with the corresponding AE-T -Mg systems [33].…”

Synergistic Geometrical and Electronic Features in the Intermetallic Phases Ca2AgM2, Ca2MgM2, and Ca2GaM2 (M = Pd, Pt)

“…Hence, in these phases the shortest Ca-Mg and Ca-Ag distances (Table 4) are smaller than the sums of atomic radii of 3.57 and 3.41 Å, [24] respectively, but similar distances are reported in CaMg 2 Pd [Ca-Pd: 3.383-3.482(2) Å]. [25] Partial mixing of Mg and Ag in Ca 5 MgAgGe 5 also results in Ca-Ag/Mg distances between 3.18 and 3.30 Å. [26] The bridging atoms, Mg or Ag, are in turn surrounded by eight Ca in their second coordination sphere in a strongly distorted square prismatic arrangement ( Figure 1c).…”

“…More interestingly, the Mg-Pd distances of 2.982 Å in Tb 2 MgPd 2 and 3.034 Å in Nd 2 MgPd 2 are also much longer than in Ca 2 MgPd 2 and agree with the sum of atomic radii (2.98 Å). Pd-Mg distances of 2.776 and 2.786(2) Å are reported in CaMg 2 Pd (YPd 2 Si type) [25] and Pt-Mg distances between 2.75 and 2.94 Å in SrMgPt (TiNiSi type). [28] Description of the missing phases Ca 2 M 2 Ga (M = Pd, Pt) became even more warranted after the surprising discovery that the two Ge analogues Ca 2 Pd 2 Ge (orthorhombic Fdd2) and Ca 2 Pt 2 Ge (monoclinic C2/c) are not isotypic.…”