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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Na(CuS)4 by Materials Project

Na(CuS)4 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Na1+ is bonded to six equivalent S2- atoms to form NaS6 octahedra that share corners with six equivalent CuS4 tetrahedra and edges with six equivalent NaS6 octahedra. All Na–S bond lengths are 2.93 Å. There are two inequivalent Cu+1.75+ sites. In the first Cu+1.75+ site, Cu+1.75+ is bonded to four S2- atoms to form CuS4 tetrahedra that share corners with three equivalent NaS6 octahedra, corners with three equivalent SCu3S tetrahedra, and corners with six equivalent CuS4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. There are three shorter (2.33 Å) and one longer (2.34 Å) Cu–S bond lengths. In the second Cu+1.75+ site, Cu+1.75+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Cu–S bond lengths are 2.23 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to three equivalent Cu+1.75+ and one S2- atom to form SCu3S tetrahedra that share corners with three equivalent CuS4 tetrahedra and corners with six equivalent SCu3S tetrahedra. The S–S bond length is 2.11 Å. In the second S2- site, S2- is bonded in a 7-coordinate geometry to three equivalent Na1+ and four Cu+1.75+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3(CuS)4 by Materials Project

Na3Cu4S4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing NaS6 octahedra. The corner-sharing octahedra tilt angles range from 39–57°. There are a spread of Na–S bond distances ranging from 2.84–3.10 Å. In the second Na1+ site, Na1+ is bonded to six S2- atoms to form a mixture of corner and edge-sharing NaS6 octahedra. The corner-sharing octahedra tilt angles range from 39–45°. There are four shorter (2.89 Å) and two longer (3.02 Å) Na–S bond lengths. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a trigonal planar geometry to three S2- atoms. There are two shorter (2.25 Å) and one longer (2.30 Å) Cu–S bond lengths. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a distorted trigonal planar geometry to three S2- atoms. All Cu–S bond lengths are 2.31 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 8-coordinate geometry to five Na1+ and three Cu+1.25+ atoms. In the second S2- site, S2- is bonded in a 7-coordinate geometry to four Na1+ and three Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Dimensional Evolution Guides Property Control in the A n Cu 4– n TiS 4 Semiconductor Series

Through progressive reduction of the three-dimensional (3D) covalent network of Cu 4 TiS 4 , we isolate seven new members of the A n Cu 4–n TiS 4 family (A = alkali metal; n = 0–4), spanning 3D, 2D, 1D, and 0D structural fragments. The dimensional reduction is rational, as it preserves the edge-sharing connectivity between [CuS 4 ] 7– and [TiS 4 ] 4– tetrahedra across the series. This structural evolution is driven by the stepwise substitution of Cu with alkali metals, guiding the formation of fragments with reduced dimensionality. The effects of “n” and “A” on the crystal structures, stabilities, electronic structures, and optoelectronic properties are profound, demonstrating that the manipulation of alkali metal size and A n Cu 4–n TiS 4 stoichiometry enables predictable variations in structure and properties. For example, the n = 0 and n = 4 end members of the A n Cu 4–n TiS 4 family set the range of achievable band gaps with 2.00 eV for Cu 4 TiS 4 , 2.60 eV for Na 4 TiS 4 , and intermediate values for the n = 1–3 members. Notably, CsCu 3 TiS 4 exhibits exceptional air stability and congruent melting, with density functional theory (DFT) calculating moderate hole and electron effective masses in specific crystallographic directions (mh = 1.24m 0 , me = 0.87m 0 ). Additionally, A 3 CuTiS 4 (A = Na, K, Rb) displays direct band gap behavior and long photoluminescence lifetimes of 2.3–8.6 μs, and K 3 CuTiS 4 has a PLQY of 5.19%. These findings underscore the potential of the A n Cu 4–n TiS 4 family for applications in optoelectronics and demonstrate widely applicable design concepts that unveil rational stoichiometries within a given composition space to generate a series of crystal structures related through an evolving covalent dimensionality that corresponds to a predictable electronic structure and property progression.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Node Distortions as a Means of Defect Engineering in Zr-Based MOFs

Defect engineering in Zr-based metal–organic frameworks (Zr-MOFs) has focused primarily on missing-linker defects. However, recent studies suggest that node dehydroxylation–which creates distortions and coordinatively unsaturated Zr sites (Zr cus )–may have a more significant impact on properties. The present work uses pair distribution function (PDF) and thermogravimetric analysis coupled with systematic defect manipulation to study the effect of node dehydroxylation and missing-linker defects in UiO-66. By employing rapid heat treatment (RHT) under humid flow, we tracked the transition from high-symmetry [Zr 6 O 4 (OH) 4 ] 12+ to distorted [Zr 6 O 6 ] 12+ nodes. This structural evolution significantly improves As(V) uptake, whereas increasing the number of missing linkers–via chemical treatment or RHT of mixed-ligand frameworks–fails to enhance performance. Crucially, our detection of distorted nodes in as-synthesized UiO-66 also raises the possibility that these defects were silently present in many earlier studies that span various applications, where their role in governing performance may have been inadvertently overlooked. The present study challenges the prevailing “missing-linker” paradigm and establishes cluster dehydroxylation as a defect-engineering strategy to enhance Lewis-acidic performance in Zr-MOFs.

Adsorption↗