New Rare-Earth/Alkaline-Earth Metal Germanides Svilen Bobev, University of Delaware, DMR 0743916.
During our systematic investigations on the composition-structure-property relationships of novel intermetallic compounds, we have successfully synthesized and characterized several novel kinds of germanides. So far, we have reported on the new phases—(Sr1–xCax)5In3Ge6/(Eu1–xYbx)5In3Ge6 (x ≈ 0.7) and (Sr1–xCax)3In2Ge4/ (Sr1–xYbx)3In2Ge4 (0.4 ≤ x ≤ 0.5), which were found to exist only with mixed cations. Their structures are based on fused InGe4 tetrahedra and Ge chains with intricate topology of cis- and trans-bonds. Similar Ge chains with π-delocalization of the Ge p-orbitals, have also been observed in the Li-containing compounds -Sr2LiGe3 and Eu2LiGe3. In these two instances, the special characteristics of the Li metal—its high ionic potential in particular—have been attributed as a key to the formation of such chains. Following this hypothesis, we set out to investigate other possible structures where similar Ge bonding patterns exist. Drawing on the structural analogies between the [Ge2] chains in (Sr1–xCax)3In2Ge4 and the Li-containing Sr2LiGe3, it was thought that small amounts of Li can be used to fine-tune the number of valence electrons in the compounds under consideration. These studies, however, did not yield the sought-after phases. Instead, the phases ALi1–xInxGe2 (0 ≤ x ≤ 0.1) and A2(Li1–xInx)2Ge3 (x ≈ 0.3) were obtained (A = Sr, Ba, Eu). With established the single-crystal structures of these two types of closely related intermetallics, where structure tunability here is provided through variations of In (or Mg) and Li. We also discussed the correlations between the crystal structures with compositions, as well as the band structures, calculated using the TB-LMTO-ASA method.
You, T.-S.; Bobev, S.J. Solid State Chem. 2010, 183, 1285
HIGHLIGHTS from 1-August-2010 – 1-August-2011
Dissemination of the results
Two papers have been presented by N.-T. Suen and S.-P. Guo at the 26th Rare-Earth Research Conference, held in June 2011 in Santa Fe, NM. The P.I. gave an invited talk at the 240th ACS National Meeting, Boston, MA. Symposium Title: (INOR007) Luminescence and Magnetism of Lanthanide-Containing Materials
Two full papers have been published in Journal of Solid State Chemistry; one of the two (presented herein) was selected as a cover page for the Journal. A structure report has been sent to Acta Crystallogr.
Undergraduate students participated in a campus-wide Undergraduate research symposium.
Education and Mentoring
-Matt Broda (Delaware – BS’11)
-Chauntae Tyson (Delaware)
-Greg Darone (Delaware)
Nian-Tzu Suen – a 2nd year graduate student is working on the project since March 2010.
- Dr. Sheng-Ping Guo was recruited and started work on the project effective January 1, 2011.