Spinel type twins of the new cubic Er₆Zn₂₃Ge compound

Abstract

The crystal structure of the new Er6Zn23Ge intermetallic compound was established by X-ray diffraction analysis on a twinned crystal (space group Fm3¯m, Wyckoff sequence: f2edba, cF120-Zr6Zn23Si, a=12.7726(6) Å). The crystal is composed of two nearly equal size domains, whose mutual orientation is described by a 180° rotation around the cubic [111] axis, i.e. a spinel-type twinning law, not common for intermetallics. Applying the nanocluster approach, Er6Ge octahedra and centered two-shell Zn45 clusters were found as structural building blocks, filling the crystal space in a NaCl-like arrangement. This description was adopted to interpret the twinning in terms of stacking faults in the fcc cubic close packed arrangement. Moreover, the assembly of the nanocluster units is proposed as a possible mechanism for crystal growth and twin formation, in agreement with the principle of the interface energy minimization. Experimental conditions such as supersaturation and co-formation of other phases are also considered as favorable factors for Er6Zn23Ge twin formation

Synthesis and structure determination of Ce6Cd23Te: a new chalcogen-containing member of theRE6Cd23T family (REis a rare-earth metal and T is a late group 14, 15 and 16 element)

“…In addition to our previous report on the RE 6 Cd 23 T series of compounds, with RE being La-Nd, Sm, and Gd, and T being Sn, Pb, Sb, and Bi (Desroches & Bobev, 2017), the crystal ISSN 2053ISSN -2296 # 2017 International Union of Crystallography chemistry of the Mg-based RE 6 Mg 23 T counterparts has also been established (Wrubl et al, 2016), in addition to that of La 6 Mg 23 Si and Er 6 Zn 23 Ge (De Negri et al, 2009;Solohka et al, 2016). In addition to our previous report on the RE 6 Cd 23 T series of compounds, with RE being La-Nd, Sm, and Gd, and T being Sn, Pb, Sb, and Bi (Desroches & Bobev, 2017), the crystal ISSN 2053ISSN -2296 # 2017 International Union of Crystallography chemistry of the Mg-based RE 6 Mg 23 T counterparts has also been established (Wrubl et al, 2016), in addition to that of La 6 Mg 23 Si and Er 6 Zn 23 Ge (De Negri et al, 2009;Solohka et al, 2016).…”

“…The discovery of Er 6 Zn 23 Ge (Solohka et al, 2016) demonstrates that this may be possible with smaller interstitial atoms, though alternative synthetic routes may need to be taken from the one employed in this work. With this in mind, our next target will be the expansion of the series into the latter half of the lanthanide metals.…”