Unexpected Magnetism in Alkaline Earth Monosilicides

Reyes, Eduardo Cuervo; Stalder, Elizabeth Diane; Mensing, Christian; Budnyk, Serhiy; Nesper, Reinhard

doi:10.1021/jp106169h

Cited by 20 publications

(17 citation statements)

References 36 publications

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“…Motifs I (Figure 2, left) are planar zigzag chains formed by the tin atoms Sn(3) and Sn(4), which are running along the [001] direction at 0,0, z and 1/2,1/2, z (Figure 1). This structure element is also found in the binary stannides EuSn,37 CaSn,38 and SrSn39 (CrB structure type), which are formally (see discussion in references8,9) electron precise Zintl phases exhibiting two‐bonded 2b Sn 2– anions. In contrast to the simple monostannides, which contain two‐bonded tin exclusively, only the Sn(4) atoms are two‐bonded in the title compounds, Sn(3) in addition is bound to two Al(2) atoms of motif III and thus exhibits an overall tetrahedral surrounding.…”

Section: Resultsmentioning

confidence: 63%

Electrochemical Reduction of Carbon Dioxide to Formic Acid

et al. 2014

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This Review provides an overview of electrochemical techniques that are implemented in addressing gaseous CO2 towards the synthesis of a particular fuel (i.e. formic acid). The electrochemical reaction mechanism, as well as the advancement of electrodes, catalyst materials, and reactor designs are reviewed and discussed. To date, the electrolytic cell is the dominant reaction site and, based on which, various catalysts have been proposed and researched. In addition, relevant work regarding reactor design optimization for the purpose of alleviating restrictions of the current CO2 electrochemical reduction system are summarized, including low reactant‐transfer rate, high reaction overpotential, and low product selectivity. The use of microfluidic techniques to build microscale electrochemical reactors is identified to be highly promising to largely increase the electrochemical performance. Finally, future challenges and opportunities of electrochemical reduction of CO2 are discussed.

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Section: Resultsmentioning

confidence: 63%

Electrochemical Reduction of Carbon Dioxide to Formic Acid

et al. 2014

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“…A real energy gap at the Fermi level is not expected because the binary parent structure CaGe is known to be metallic, although formally a Zintl phase. 46 However, a pseudogap was expected above E F at 136 ve/cell (or 44 ve/f.u), as suggested by the Zintl concept. For the two-electron-deficient phases Ae 7 Ge 6 , a (pseudo)gap is always observed in the DOS plot above E F at the Zintl limit of electron count.…”

Section: ■ Results and Discussionmentioning

confidence: 91%

Valence State Driven Site Preference in the Quaternary Compound Ca₅MgAgGe₅: An Electron-Deficient Phase with Optimized Bonding

et al. 2014

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The quaternary phase Ca 5 Mg 0.95 Ag 1.05(1) Ge 5 (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma -Wyckoff sequence c 12 with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å 3 , Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R 2+n T 2 X 2+n , previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm -Wyckoff sequence f 5 c 2 . The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO electronic structure calculations indicate electronic stabilization and overall bonding optimization in the polyanionic network. Other stability factors beyond the Zintl concept that may account for the electronic stabilization are discussed. (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma − Wyckoff sequence c 12 with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å 3 , Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R 2+n T 2 X 2+n , previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm − Wyckoff sequence f 5 c 2 . The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO ...

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“…9(2) f -Sn (42) 293. 9(2) f -Sn (42) 297.6(3) g -La (17) 328.2(2) -La (12) 330.1(2) -La (11) 339.4(2) -La(18) 332.8(2) -La (10) 343.0(2) -La (19) 333.4(2) -La (12) 350.1(2) -La(18) 344.5(2) -La (13) 354.8(2) -La(13) 346.5(2) -La (13) 357.5(2) -La(10) 358.1(2) -La (11) 364.0(2) 2 + 7 -La (13) (2) 315.0(2) -La (19) 326.0(2) 2× -La (15) 328.0(2) 2× -La (18) 326.6(2) 2× -La (19) 328.3(2) 2× -La (6) In addition, the Ge/Sn atoms M(64) are formally also part of the slabs A, as they are crosslinking the eight-membered rings of two adjacent slabs B to form infinite chains running along the c axis, i.e. through the slabs A (cf.…”

Section: Structure Descriptionmentioning

confidence: 99%

“…Both border phases, LaGe and LaSn, are dimorphic exhibiting the simple FeB (LaGe [1][2][3][4]) and CrB (LaSn [5]) structure types at higher temperatures. Despite their simple crystal structures, which exhibit planar all-trans zig-zag chains in different orientations to each other, the chemical bonding in these compounds is still puzzling and has therefore been the topic of several recent experimental and theoretical studies [4,[6][7][8][9]. The low-temperature (l.t.)…”

Section: Introductionmentioning

confidence: 99%