Combined computational and experimental investigation of the La2CuO4-x S x (0 ≤ x ≤ 4) quaternary system.

The lack of a mechanistic framework for chemical reactions forming inorganic extended solids presents a challenge to accelerated materials discovery. We demonstrate here a combined computational and experimental methodology to tackle this problem, in which in situ X-ray diffraction measurements monitor solid-state reactions and deduce reaction pathways, while theoretical computations rationalize reaction energetics. The method has been applied to the La2CuO4-x S x (0 ≤ x ≤ 4) quaternary system, following an earlier prediction that enhanced superconductivity could be found in these new lanthanum copper(II) oxysulfide compounds. In situ diffraction measurements show that reactants containing Cu(II) and S(2-) ions undergo redox reactions, leaving their ions in oxidation states that are incompatible with forming the desired new compounds. Computations of the reaction energies confirm that the observed synthetic pathways are indeed favored over those that would hypothetically form the suggested compounds. The consistency between computation and experiment in the La2CuO4-x S x system suggests a role for predictive theory: to identify and to explicate new synthetic routes for forming predicted compounds.

High ionic conductivity materials Li3YBr6and Li3LaBr6for solid-state batteries: first-principles calculations.

High ionic conductivity solid-state electrolytes are essential for powerful solid-state lithium-ion batteries. With density functional theory andab initiomolecular dynamics simulations, we investigated the crystal structures of Li3YBr6and Li3LaBr6. The lowest energy configurations with uniform distribution of lithium ions were identified. Both materials have wide electrochemical stability windows (ESW): 2.64 V and 2.57 V, respectively. The experimental ESW for Li3YBr6is 2.50 V. Through extrapolating various temperature diffusion results, the conductivity of Li3YBr6was obtained at room temperature, approximately 3.9 mS cm-1, which is comparable to the experimental value 3.3 mS cm-1. Li3LaBr6has a higher conductivity, a 100% increase compared with Li3YBr6. The activation energies of Li3YBr6and Li3LaBr6through the Arrhenius plot are 0.26 eV and 0.24 eV, respectively, which is also close to the experimental value of 0.30 eV for Li3YBr6. This research explored high ionic conductivity halide materials and will contribute to developing solid-state lithium-ion batteries.

Synthesis and crystal structure of La21Cr8-2a Al b Ge7-b C12 [a = 0.22†(2) and b = 0.758†(19)].

Single crystals of a new multinary chromium carbide, La21Cr8-2a Al b Ge7-b C12 (henicosa-lanthanum octa-chromium aluminium hexa-germanium dodeca-carbide), were grown from an La-rich self flux and were characterized by single-crystal X-ray diffraction. The face-centered cubic crystal structure is composed of isolated and geometrically frustrated regular Cr tetra-hedra that are co-centered within regular C octa-hedra. These mutually separated Cr4-aC6 clusters are distributed throughout a three-dimensional framework of Al, Ge, and La. The title compound is isotypic with La21-δMn8X7C12 and R21Fe8X7C12 (R = La, Ce, Pr; X = Al, Bi, Ge, Sn, Sb, Te) and represents the first example of a Cr-based compound with this structure-type.