Ternary arsenides Zr(Si As1−)As with PbCl2-type (0 ≤x≤ 0.4) and PbFCl-type (x= 0.6) structures

On the existence of ZrAs2 and ternary extension Zr(GexAs1−x)As (0≤x≤0.4)

“…The ternary extension Zr(Ge x As 1−x )As forms up to x = ∼0.4, with Ge atoms entering preferentially into the interior sites of four-atom-wide anionic ribbons in this structure. This solid solution range is similar as observed previously in Zr(Si x As 1−x )As but is much wider than in Zr(Si x Sb 1−x )Sb [1,5]. Although the substitution of Si or Ge into ZrAs 2 seems to originate for the same reasons (strengthened anion-anion bonding) as for the impurity stabilization of "␤-ZrSb 2 ", there are subtle differences in these systems that may need to be explored further.…”

“…Finally, a similar treatment as above in which Ge and As atoms were allowed to disorder over both sites was successful in resolving a preferential occupation of 37(8)% Ge and 63(8)% As on the first site, and 8(9)% Ge and 91(9)% As on the second site. Taking into account the large uncertainties in these occupancies, we assumed that only the first site was disordered with Ge and As atoms, whereas the second site was occupied exclusively by As atoms, in accordance with related structures such as Zr(Ge0.2Sb0.8)Sb and Zr(Si0.4As0.6)As in which the Tt atom enters only one of the two anion sites [1,5]. The final refinement led to a formula of "Zr(Ge 0.33(6) As0.67)As", which we simplify to Zr(Ge0.3As0.7)As in subsequent discussion.…”

“…Cell parameters and atomic positions were taken from the crystal structures of ZrAs2 and Zr(Ge0.3As0.7)As. The ordered Zr(Ge0.5As0.5)As model (in space group Pmc21), based on one previously considered for Zr(Si0.5As0.5)As [5], involves an alternation of Ge and As atoms within zigzag chains parallel to b. The basis sets consisted of Zr 5s/5p/4d/4f, Ge 4s/4p/4d, and As 4s/4p/4d orbitals, with the Zr 4f, Ge 4d, and As 4d orbitals being downfolded.…”

“…In an early structure determination, the possibility of an As-deficient formula, ZrAs 2−x , could not be excluded [4]. In more recent investigations, we have established that, like the antimonides, the ternary arsenides Zr(Si x As 1−x )As form a PbCl 2 -type phase at lower Si content (0 ≤ x ≤ 0.4) (on the assumption that ZrAs 2 does exist) and a PbFCl-type phase at higher Si content (x = 0.6) [5].…”

Quaternary Germanide Arsenides ZrCuGeAs and HfCuGeAs

“…The derivation of the ZrCuSiAs‐type as a filled PbFCl‐type structure was recognized early on 2. Indeed, there do exist ternary PbFCl‐type arsenides Zr(Si 0.6 As 0.4 )As and Hf(Si 0.5 As 0.5 )Asthat could be regarded as the host structures of ZrCuSiAs and HfCuSiAs, respectively, in which tetrahedral voids are filled by copper atoms 7–9. However, the relationship is not strict because, as implied by the formulas, the silicon and arsenic atoms are partially disordered in the ternary compounds but ordered in the quaternary compounds.…”