Browsing by Author "Klein, Wilhelm"
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- Aliovalent substitution in phosphide-based materials – Crystal structures of Na10AlTaP6 and Na3GaP2 featuring edge-sharing EP4 tetrahedra (E=Al/Ta and Ga)
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-09-27) Restle, Tassilo M. F.; Zeitz, Sabine; Meyer, Jan; Klein, Wilhelm; Raudaschl-Sieber, Gabriele; Karttunen, Antti J.; Fässler, Thomas F.Recently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. Much less is known about the corresponding sodium-containing compounds, and during investigations aiming for sodium phosphidotrielates, two new compounds have been obtained. The sodium phosphidoaluminumtantalate Na10AlTaP6, at first obtained as a by-product from the reaction with the container material, crystallizes in the monoclinic space group P21/n (no. 14) with lattice parameters of a=8.0790(3) Å, b=7.3489(2) Å, c=13.2054(4) Å, and β=90.773(2)°. The crystal structure contains dimers of edge-sharing [(Al0.5Ta0.5)P4] tetrahedra with a mixed Al/Ta site. DFT calculations support the presence of this type of arrangement instead of homonuclear Al2P6 or Ta2P6 dimers. The 31P and 23Na MAS NMR as well as the Raman spectra confirm the structure model. The assignment of the chemical shifts is confirmed applying the DFT-PBE method on the basis of the ordered structural model with mixed AlTaP6 dimers. The sodium phosphidogallate Na3GaP2 crystallizes in the orthorhombic space group Ibam (no. 72) with lattice parameters of a=13.081(3) Å, b=6.728(1) Å, and c=6.211(1) Å and is isotypic to Na3AlP2. Na3GaP2 exhibits linear chains of edge-sharing 1∞[GaP4/2] tetrahedra. For both compounds band structure calculations predict indirect band gaps of 2.9 eV. - Anionic Siliconoids from Zintl Phases: R3Si9 − with Six and R2Si9 2− with Seven Unsubstituted Exposed Silicon Cluster Atoms (R=Si(tBu)2H)
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2018-12-20) Schiegerl, Lorenz J.; Karttunen, Antti J.; Klein, Wilhelm; Fässler, Thomas F.Neutral and anionic silicon clusters (siliconoids) are regarded as important model systems for bulk silicon surfaces. For 25 years their formation from binary alkali metal silicide phases has been proposed, but experimentally never realized. Herein the silylation of a silicide, leading to the anionic siliconoids (Si(tBu)2H)3Si9 − (1 a) and (Si(tBu)2H)2Si9 2− (2 a) with the highest known number of ligand-free silicon atoms is reported for the first time. The new anions are obtained in a one-step reaction of K12Si17/NH3(liq.) and Si(tBu)2HCl/THF. Electrospray ionization spectrometry and 1H, 13C, 29Si, as well as 29Si-HMBC (heteronuclear multiple bond correlation) NMR spectroscopy, confirm the attachment of three silyl groups at a [Si9]4− cluster under formation of 1 a, in accordance with calculated NMR shifts. During crystal growth the siliconoid di-anion 2 a is formed. The single-crystal X-ray structure determination reveals that two silyl groups are connected to the deltahedral Si9 cluster core, revealing seven unsubstituted exposed silicon cluster atoms with a hemispheroidal coordination. The negative charges −1 and −2 are delocalized over the six and seven siliconoid Si atoms in 1 a and 2 a, respectively. - Direct Band Gap Semiconductors with Two- and Three-Dimensional Triel-Phosphide Frameworks (Triel=Al, Ga, In)
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-03-25) Restle, Tassilo M.F.; Zeitz, Sabine; Stanley, Philip M.; Karttunen, Antti J.; Meyer, Jan; Raudaschl-Sieber, Gabriele; Klein, Wilhelm; Fässler, Thomas F.Recently, several ternary phosphidotrielates and -tetrelates have been investigated with respect to their very good ionic conductivity, while less focus was pointed towards their electronic structures. Here, we report on a novel series of compounds, in which several members possess direct band gaps. We investigated the known compounds Li3AlP2, Li3GaP2, Li3InP2, and Na3InP2 and describe the synthesis and the crystal structure of novel Na3In2P3. For all mentioned phosphidotrielates reflectance UV-Vis measurements reveal direct band gaps in the visible light region with decreasing band gaps in the series: Li3AlP2 (2.45 eV), Li3GaP2 (2.18 eV), Li3InP2 (1.99 eV), Na3InP2 (1.37 eV), and Na3In2P3 (1.27 eV). All direct band gaps are confirmed by quantum chemical calculations. The unexpected property occurs despite different structure types. As a common feature all compounds contain EP4 tetrahedra, which share exclusively vertices for E=In and vertices as well as edges for E=Al and Ga. The structure of the novel Na3In2P3 is built up by a polyanionic framework of six-membered rings of corner-sharing InP4 tetrahedra. As a result, the newly designed semiconductors with direct band gaps are suitable for optoelectronic applications, and they can provide significant guidance for the design of new functional semiconductors. - Silicon clusters with six and seven unsubstituted vertices: Via a two-step reaction from elemental silicon
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-01-01) Schiegerl, Lorenz J.; Karttunen, Antti J.; Klein, Wilhelm; Fässler, Thomas F.Unsaturated silicon clusters with only partial substitution, and thus, "naked" Si atoms are well studied species as they are proposed intermediates in gas-phase deposition processes. Although a remarkable number of stable molecular clusters has been reported, they are typically still obtained by multi-step syntheses. Herein we introduce a newly developed synthetic approach which led to the formation of the anionic species {Si(TMS)3}3Si9- (1a) and {Si(TMS)3}2Si92- (1b), and an extension of this synthetic protocol resulted in the first covalent attachment of ligands through metal atoms to these clusters, (SnCy3)3Si9- (2a) and (SnCy3)2Si92- (2b). The influence of the substituents on the electron localization in the central Si9 unit is analyzed by means of intrinsic bond orbital (IBO) analysis and partial atomic charge distribution. The IBO analyses reveal a new type of delocalization including 5-center-6-electron besides 3-center-2-electron bonds. The Raman spectra of 1b and 2b allow an assignment of the Si-Si intra-cluster vibrations by comparison to calculated (DFT-PBE0) spectra. The anions are formed in a one-step synthesis from binary K12Si17 which can easily be obtained by fusing the elements K and Si. The anions are characterized by ESI mass spectrometry and comprehensive NMR studies (1H, 13C, 29Si, 119Sn). Attempts to crystallize 1a and 2a as their (K-222crypt)+ salts yielded after the loss of one of the substituents single crystals containing 1b and 2b. The single crystal X-ray structure analyses reveal the presence of anionic siliconoids with surfaces of seven unsubstituted silicon atoms.