New Rare-Earth/Alkaline-Earth Metal Germanides Svilen Bobev, University of Delaware, DMR 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—(Sr 1–x Ca x ) 5 In 3 Ge 6 /(Eu 1– x Yb x ) 5 In 3 Ge 6 (x ≈ 0.7) and (Sr 1–x Ca x ) 3 In 2 Ge 4 / (Sr 1–x Yb x ) 3 In 2 Ge 4 (0.4 ≤ x ≤ 0.5), which were found to exist only with mixed cations. Their structures are based on fused InGe 4 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  - Sr 2 LiGe 3 and Eu 2 LiGe 3. 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 [Ge 2 ] chains in (Sr 1–x Ca x ) 3 In 2 Ge 4 and the Li-containing Sr 2 LiGe 3, 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 ALi 1–x In x Ge 2 (0 ≤ x ≤ 0.1) and A 2 (Li 1–x In x ) 2 Ge 3 (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

New Rare-Earth/Alkaline-Earth Metal Germanides Svilen Bobev, University of Delaware, DMR Education and Mentoring Undergraduate Participation: -Matt Broda (Delaware – BS’11) -Chauntae Tyson (Delaware) -Greg Darone (Delaware) Graduate Participation: Nian-Tzu Suen – a 2 nd year graduate student is working on the project since March Post-doctoral Participation: - Dr. Sheng-Ping Guo was recruited and started work on the project effective January 1, 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 26 th Rare-Earth Research Conference, held in June 2011 in Santa Fe, NM. The P.I. gave an invited talk at the 240 th 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.