[Ge₂]⁴⁻Dumbbells with Very Short Ge−Ge Distances in the Zintl Phase Li₃NaGe₂: A Solid-State Equivalent to Molecular O₂

The novel ternary Zintl phase Li3NaGe2 comprises alkali-metal cations and [Ge2]4− dumbbells. The diatomic [Ge2]4− unit is characterized by the shortest Ge−Ge distance (2.390(1) Å) ever observed in a Zintl phase and thus represents the first Ge=Ge double bond under such conditions, as also suggested by the (8−N) rule. Raman measurements support these findings. The multiple-bond character is confirmed by electronic-structure calculations, and an upfield 6Li NMR shift of −10.0 ppm, which was assigned to the Li cations surrounded by the π systems of three Ge dumbbells, further underlines this interpretation. For the unperturbed, ligand-free dumbbell in Li3NaGe2, the π- bonding py and pz orbitals are degenerate as in molecular oxygen, which has singly occupied orbitals. The partially filled π-type bands of the neat solid Li3NaGe2 cross the Fermi level, resulting in metallic properties. Li3NaGe2 was synthesized from the elements as well as from binary reactants and subsequently characterized crystallographically.O.P. acknowledges support from a Marie Skłodowska-Curie Individual Fellowship. L.M.S. is further grateful to the Fonds der Chemischen Industrie and the Studienstiftung des deutschen Volkes for her fellowships. A.J.K. gratefully acknowledges funding from the Alfred Kordelin Foundation and computational resources from CSC – the Finnish IT Center for Science.This is the accepted manuscript. The final version is available at http://onlinelibrary.wiley.com/wol1/doi/10.1002/ange.201508044/abstract

Unravelling Local Atomic Order of the Anionic Sublattice in M(Al1-x Gax )4 with M=Sr and Ba by Using NMR Spectroscopy and Quantum Mechanical Modelling.

The quasibinary section of the intermetallic phases MAl4 and MGa4 with M=Sr and Ba have been characterised by means of X-ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al1-x Gax )4 with M=Sr and Ba. These structures crystallise in the BaAl4 structure type with four- and five-bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state 27 Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al1-x Gax )4 with M=Sr and Ba and 0.925≤x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, 27 Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)-Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results.Excellence Initiativ

Sodium Intercalation Mechanism of 3.8 v Class Alluaudite Sodium Iron Sulfate

Alluaudite sodium iron sulfate Na$_{2+2x}$Fe$_{2−x}$(SO$_4$)$_3$ is one of the most promising candidates for a Na-ion battery cathode material with earth-abundant elements; it exhibits the highest potential among any Fe$^{3+}$/Fe$^{2+}$ redox reactions (3.8 V vs Na/Na$^+$ ), good cycle performance, and high rate capability. However, the reaction mechanism during electrochemical charging/discharging processes is still not understood. Here, we surveyed the intercalation mechanism via synchrotron X-ray diffraction (XRD), $^{23}$Na nuclear magnetic resonance (NMR), density functional theory (DFT) calculations, X-ray absorption near edge structure (XANES), and Mössbauer spectroscopy. Throughout charging/discharging processes, the structure undergoes a reversible, single-phase (solid solution) reaction based on a Fe$^{3+}$/Fe$^{2+}$ redox reaction with a small volume change of ca. 3.5% after an initial structural rearrangement upon the first charging process, where a small amount of Fe irreversibly migrates from the original site to a Na site. Sodium extraction occurs in a sequential manner at various Na sites in the structure at their specific voltage regions.The present work was financially supported from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) under the “Element Strategy Initiative for Catalysts & Batteries” (ESICB) project. The synchrotron XRD experiments were performed under KEK-PF User Program (No. 2013G670). Crystal structures and the Fourier difference maps were drawn by VESTA.65 G.O. acknowledges financial support from JSPS Research Fellowships under “Materials Education Program for the Future Leaders in Research, Industry, and Technology” (MERIT) project. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 655444 (O.P.). R.P. gratefully acknowledges financial support through the Marie Curie Actions People Program of the EU’s Seventh Frame work Program (FP7/2007-2013), under the grant agreement n.317127, the ‘pNMR project’. K.J.G. gratefully acknowledges funding from The Winston Churchill Foundation of the United States and the Herchel Smith Scholarship. This work made use of the facilities of the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.This is the final version of the article. It first appeared from American Chemical Society via http://dx.doi.org/10.1021/acs.chemmater.6b0109

Structural and Mechanistic Insights into Fast Lithium-Ion Conduction in Li4SiO4-Li3PO4 Solid Electrolytes.

Solid electrolytes that are chemically stable and have a high ionic conductivity would dramatically enhance the safety and operating lifespan of rechargeable lithium batteries. Here, we apply a multi-technique approach to the Li-ion conducting system (1-z)Li4SiO4-(z)Li3PO4 with the aim of developing a solid electrolyte with enhanced ionic conductivity. Previously unidentified superstructure and immiscibility features in high-purity samples are characterized by X-ray and neutron diffraction across a range of compositions (z = 0.0-1.0). Ionic conductivities from AC impedance measurements and large-scale molecular dynamics (MD) simulations are in good agreement, showing very low values in the parent phases (Li4SiO4 and Li3PO4) but orders of magnitude higher conductivities (10(-3) S/cm at 573 K) in the mixed compositions. The MD simulations reveal new mechanistic insights into the mixed Si/P compositions in which Li-ion conduction occurs through 3D pathways and a cooperative interstitial mechanism; such correlated motion is a key factor in promoting high ionic conductivity. Solid-state (6)Li, (7)Li, and (31)P NMR experiments reveal enhanced local Li-ion dynamics and atomic disorder in the solid solutions, which are correlated to the ionic diffusivity. These unique insights will be valuable in developing strategies to optimize the ionic conductivity in this system and to identify next-generation solid electrolytes.The ALISTORE ERI and CNRS are acknowledged for supporting Y.D. through a joint Ph.D. scholarship between Picardie (France) and Bath (UK). The authors thank D. Sheptyakov (PSI, Switzerland) and M. Bianchini (ILL-Grenoble, France) for assistance with neutron diffraction experiments, and M. T. Dunstan (Cambridge, UK) for assistance with NMR experiments. Financial support from the EPSRC Energy Materials Programme (Grant EP/K016288) is gratefully acknowledged. The HPC Materials Chemistry Consortium (EP/L000202) allowed use of the ARCHER facilities. O.P. and S.E. acknowledge support from a Marie Skłodowska-Curie Fellowship (H2020-MSCA-IF-2014-EF, no. 655444) and an ERASMUS+ scholarship, respectively.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/jacs.5b0444

Towards an atomistic understanding of disordered carbon electrode materials.

Disordered nanoporous and "hard" carbons are widely used in batteries and supercapacitors, but their atomic structures are poorly determined. Here, we combine machine learning and DFT to obtain new atomistic insight into carbonaceous energy materials. We study structural models of porous and graphitic carbons, and Na intercalation as relevant for sodium-ion batteries

A Functional Role for Modality-Specific Perceptual Systems in Conceptual Representations

Theories of embodied cognition suggest that conceptual processing relies on the same neural resources that are utilized for perception and action. Evidence for these perceptual simulations comes from neuroimaging and behavioural research, such as demonstrations of somatotopic motor cortex activations following the presentation of action-related words, or facilitation of grasp responses following presentation of object names. However, the interpretation of such effects has been called into question by suggestions that neural activation in modality-specific sensorimotor regions may be epiphenomenal, and merely the result of spreading activations from “disembodied”, abstracted, symbolic representations. Here, we present two studies that focus on the perceptual modalities of touch and proprioception. We show that in a timed object-comparison task, concurrent tactile or proprioceptive stimulation to the hands facilitates conceptual processing relative to control stimulation. This facilitation occurs only for small, manipulable objects, where tactile and proprioceptive information form part of the multimodal perceptual experience of interacting with such objects, but facilitation is not observed for large, nonmanipulable objects where such perceptual information is uninformative. Importantly, these facilitation effects are independent of motor and action planning, and indicate that modality-specific perceptual information plays a functionally constitutive role in our mental representations of objects, which supports embodied assumptions that concepts are grounded in the same neural systems that govern perception and action

Racial differences in systemic sclerosis disease presentation: a European Scleroderma Trials and Research group study

Objectives. Racial factors play a significant role in SSc. We evaluated differences in SSc presentations between white patients (WP), Asian patients (AP) and black patients (BP) and analysed the effects of geographical locations.Methods. SSc characteristics of patients from the EUSTAR cohort were cross-sectionally compared across racial groups using survival and multiple logistic regression analyses.Results. The study included 9162 WP, 341 AP and 181 BP. AP developed the first non-RP feature faster than WP but slower than BP. AP were less frequently anti-centromere (ACA; odds ratio (OR) = 0.4, P < 0.001) and more frequently anti-topoisomerase-I autoantibodies (ATA) positive (OR = 1.2, P = 0.068), while BP were less likely to be ACA and ATA positive than were WP [OR(ACA) = 0.3, P < 0.001; OR(ATA) = 0.5, P = 0.020]. AP had less often (OR = 0.7, P = 0.06) and BP more often (OR = 2.7, P < 0.001) diffuse skin involvement than had WP.AP and BP were more likely to have pulmonary hypertension [OR(AP) = 2.6, P < 0.001; OR(BP) = 2.7, P = 0.03 vs WP] and a reduced forced vital capacity [OR(AP) = 2.5, P < 0.001; OR(BP) = 2.4, P < 0.004] than were WP. AP more often had an impaired diffusing capacity of the lung than had BP and WP [OR(AP vs BP) = 1.9, P = 0.038; OR(AP vs WP) = 2.4, P < 0.001]. After RP onset, AP and BP had a higher hazard to die than had WP [hazard ratio (HR) (AP) = 1.6, P = 0.011; HR(BP) = 2.1, P < 0.001].Conclusion. Compared with WP, and mostly independent of geographical location, AP have a faster and earlier disease onset with high prevalences of ATA, pulmonary hypertension and forced vital capacity impairment and higher mortality. BP had the fastest disease onset, a high prevalence of diffuse skin involvement and nominally the highest mortality

NMR-Spektroskopie an intermetallischen Phasen in den Systemen EA-Al-Ga mit EA = Ca, Sr und Ba : experimentelle und theoretische Untersuchungen der chemischen Bindung

Intermetallic phases are widely used in industrial and technical applications. Until this day, the modification of properties is still based on empiric approaches. The lack of a precise knowledge about the chemical bonding in intermetallic phases limits the target oriented synthesis of materials with designated properties. Achieving detailed information about the structure-bonding-property relationships in intermetallic phases is a necessary step to open new opportunities for applications and to increase efficiency of existing materials. Since substitutional disorder is of pronounced role concerning the properties of intermetallic phases, the impact on the local bonding situation in the systems Sr1-xBaxGa2, Sr(Al1-xGax)2, M(Al1-xGax)4 with M = Sr, Ba and Ca1-xGa2+3x as well as Ca3-xGa8+3x was investigated, respectively. The combined application of diffraction (XRD), NMR spectroscopy and quantum mechanical (QM) calculations is well suited to gain information on atomic interactions by an analysis of the electric field gradient (EFG). Within the scope of this work, a specially designed probe system for orientation dependent NMR experiments on magnetically aligned powder samples was commissioned to establish the XRD-NMR-QM approach on intermetallic phases being strongly influenced by substitutional disorder. To ensure single phase material for NMR spectroscopy, a detailed characterization of the samples was performed using X-ray diffraction, thermoanalytical and metallographic investigations. This resulted in a re-investigation of the Ga-rich part of the phase diagram Ca-Ga focussing on the intermetallic phases Ca1-xGa2+3x and Ca3-xGa8+3x. Furthermore, conclusions about the structural chemistry and miscibility of the solid solutions Sr1-xBaxGa2, Sr(Al1-xGax)2 as well as M(Al1-xGax)4 with M = Sr, Ba were achieved. Orientation dependent 27Al and 69;71Ga NMR experiments on aligned powder samples were used to analyse the local Al and Ga environments. The influence of alkaline earth metal substitution on the Ga atoms was investigated in the solid solution Sr1-xBaxGa2. NMR spectroscopy revealed two different species Ga and Ga' with similar values of the EFG. A local symmetry reduction for Ga' was proven. In the solid solution Ba(Al1-xGax)4 a significant influence of group 13 elements substitution on the bonding situation with preferred occupancy of four (4b) and five bonded (5b) Al and Ga positions was studied, respectively. In Ca1-xGa2+3x triangular Ga3 units partially substitute the Ca atoms. Different three (3b) and four bonded (4b) Ga environments could be resolved and analysed by NMR experiments. The local atomic environments could partially be modelled in superstructures enabling QM calculations of NMR coupling parameters. From that, a verification of experimental results was possible. Future studies will have to focus on an analysis of the electronic contributions dominating the EFG

NMR-Spektroskopie an intermetallischen Phasen in den Systemen EA-Al-Ga mit EA = Ca, Sr und Ba : experimentelle und theoretische Untersuchungen der chemischen Bindung

Intermetallic phases are widely used in industrial and technical applications. Until this day, the modification of properties is still based on empiric approaches. The lack of a precise knowledge about the chemical bonding in intermetallic phases limits the target oriented synthesis of materials with designated properties. Achieving detailed information about the structure-bonding-property relationships in intermetallic phases is a necessary step to open new opportunities for applications and to increase efficiency of existing materials. Since substitutional disorder is of pronounced role concerning the properties of intermetallic phases, the impact on the local bonding situation in the systems Sr1-xBaxGa2, Sr(Al1-xGax)2, M(Al1-xGax)4 with M = Sr, Ba and Ca1-xGa2+3x as well as Ca3-xGa8+3x was investigated, respectively. The combined application of diffraction (XRD), NMR spectroscopy and quantum mechanical (QM) calculations is well suited to gain information on atomic interactions by an analysis of the electric field gradient (EFG). Within the scope of this work, a specially designed probe system for orientation dependent NMR experiments on magnetically aligned powder samples was commissioned to establish the XRD-NMR-QM approach on intermetallic phases being strongly influenced by substitutional disorder. To ensure single phase material for NMR spectroscopy, a detailed characterization of the samples was performed using X-ray diffraction, thermoanalytical and metallographic investigations. This resulted in a re-investigation of the Ga-rich part of the phase diagram Ca-Ga focussing on the intermetallic phases Ca1-xGa2+3x and Ca3-xGa8+3x. Furthermore, conclusions about the structural chemistry and miscibility of the solid solutions Sr1-xBaxGa2, Sr(Al1-xGax)2 as well as M(Al1-xGax)4 with M = Sr, Ba were achieved. Orientation dependent 27Al and 69;71Ga NMR experiments on aligned powder samples were used to analyse the local Al and Ga environments. The influence of alkaline earth metal substitution on the Ga atoms was investigated in the solid solution Sr1-xBaxGa2. NMR spectroscopy revealed two different species Ga and Ga' with similar values of the EFG. A local symmetry reduction for Ga' was proven. In the solid solution Ba(Al1-xGax)4 a significant influence of group 13 elements substitution on the bonding situation with preferred occupancy of four (4b) and five bonded (5b) Al and Ga positions was studied, respectively. In Ca1-xGa2+3x triangular Ga3 units partially substitute the Ca atoms. Different three (3b) and four bonded (4b) Ga environments could be resolved and analysed by NMR experiments. The local atomic environments could partially be modelled in superstructures enabling QM calculations of NMR coupling parameters. From that, a verification of experimental results was possible. Future studies will have to focus on an analysis of the electronic contributions dominating the EFG