Incommensurately Modulated δ″-Au_1+xCd_2–xFormed by an Unquenchable Phase Transformation from the γ-Brass δ′-Phase

Abstract

The synthesis and structural determination of the compound δ"-Au(1+x)Cd(2-x) (0.07 ≤ x ≤ 0.08) is reported. The structure may be formally derived from that of ξ-CoZn13, but elemental ordering causes an incommensurate modulation as determined by single-crystal X-ray diffraction at room temperature. The compound δ"-Au(3.23)Cd(5.76) crystallizes in the monoclinic super space group C2/m(0β½)00 with lattice parameters a = 14.790(2) Å, b = 8.251(1) Å, c = 12.744(1) Å, β = 115.182(9)° and a q-vector q = (0β½), β = 0.579b*. The δ"-phase is stable up to 652(1) K.

From Laves Phases to Quasicrystal Approximants in the Na–Au–Cd System

“…These slight distortions in the distances and coplanar angles in the (Au/Cd) 5 Cd 2 pentagonal units and (Au/Cd) 4 Cd 2 hexagonal facets of the Friauf truncated polyhedra are compensated for by one another, inducing local 2D pseudo pentagonal symmetry and equivalent long-range distortion in the unit cell along the bc plane. Surprisingly, the Au/Cd–Au/Cd distances are greater (0.12 Å) than the sum of the covalent radii of Au and Cd (2.80 Å), although still within the range of observed Au–Cd distances in other Au/Cd compounds (2.74–3.18 Å). , …”

“…Surprisingly, the Au/Cd−Au/Cd distances are greater (0.12 Å) than the sum of the covalent radii of Au and Cd (2.80 Å), although still within the range of observed Au−Cd distances in other Au/Cd compounds (2.74−3.18 Å). 72,73 Electronic Structure and Chemical Bonding. Calculating the electronic structure, phonon structure, and chemical bonding for Na(Au 0.89(5) Cd 0.11(5) ) 2 , Na(Au 0.51(4) Cd 0.49(4) ) 2 , and Na 8 Au 3.53(1) Cd 13.47 (1) can provide insight into their unique structural characteristics.…”

Complex structures in the Au – Cd alloy system: Hume-Rothery mechanism as origin

“…3.1.3. Long-period superlattice Au 2 Cd-hP98 (29)(30)(31)(32)(33)(34) Along with hcp-based superlattices that have long period in c dimension such as in hP4, there are also several phases with long periods in a dimension. We consider the phase that is formed at 29 -34 at% Cd and described in Refs.…”

“…Recent structural studies of AuCd 2 alloys (high-temperature form δ″) have determined the incommensurately modulated structure described with the average cell mC72 [33]. The basic structure of δ″-AuCd 2 represents a new type; the elemental ordering causes an incommensurate modulation.…”

(3 + 1)-Dimensional commensurately modulated structure and photoluminescence properties of diborate KSbOB2O5

“…In this view, four reciprocal vectors (a*, b*, c*, q) in 3D space are considered to be the projection of four reciprocal basis vectors in 4D space. Many modulated structures have been solved properly in recent years, such as 2H-NbSe 2 , 7 [Bi 0.84 CaO 2 ] 2 [CoO 2 ] 1.69 , 8 [CaNd] 2 [Ga] 2 [Ga 2 O 7 ] 2 , 9 Lu 4 AlCu 2 -B 9 O 23 , 10 β-TcCl 2 , 11 REe 7 (RE = La, Ce, Pr, Nd, Sm), 12 Eu(Zn 1−x -Ge x ) 2 , 13 δ″-Au 1+x Cd 2−x , 14 Sr 2 Fe 2 O 5 , 15 LiFeBO 3 , 16 17 and Zr 2 Co 11 , 18 etc.…”