An official website of the United States government
Visualizing the alignment of lone pair electrons in La 3 AsS 5 Br 2 and La 5 As 2 S 9 Cl 3 to form an acentric or centrosymmetric structure
Heteroanionic chalcohalides La3AsS5Br2and La5As2S9Cl3exhibit a good example of how alignment of lone pair electrons affects the formation of acentric crystal structure.
more »
« less
- Award ID(s):
- 2316811
- PAR ID:
- 10518961
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- CrystEngComm
- Volume:
- 25
- Issue:
- 45
- ISSN:
- 1466-8033
- Page Range / eLocation ID:
- 6354 to 6360
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract 1D charge transport offers great insight into strongly correlated physics, such as Luttinger liquids, electronic instabilities, and superconductivity. Although 1D charge transport is observed in nanomaterials and quantum wires, examples in bulk crystalline solids remain elusive. In this work, it is demonstrated that spin‐orbit coupling (SOC) can act as a mechanism to induce quasi‐1D charge transport in the Ln3MPn5(Ln = lanthanide; M = transition metal; Pn = Pnictide) family. From three example compounds, La3ZrSb5, La3ZrBi5, and Sm3ZrBi5, density functional theory calculations with SOC included show a quasi‐1D Fermi surface in the bismuthide compounds, but an anisotropic 3D Fermi surface in the antimonide structure. By performing anisotropic charge transport measurements on La3ZrSb5, La3ZrBi5, and Sm3ZrBi5, it is demonstrated that SOC starkly affects their anisotropic resistivity ratios (ARR) at low temperatures, with an ARR of ≈4 in the antimonide compared to ≈9.5 and ≈22 (≈32 after magnetic ordering) in La3ZrBi5and Sm3ZrBi5, respectively. This report demonstrates the utility of spin‐orbit coupling to induce quasi‐low‐dimensional Fermi surfaces in anisotropic crystal structures, and provides a template for examining other systems.more » « less
-
Abstract Heat capacities and enthalpies of formation of BaGd2O4were determined by high‐temperature differential scanning calorimetry and high‐temperature oxide melt solution calorimetry, respectively. Thermodynamic stability of BaLn2O4compounds increases with decreasing Ln3+ionic radius. Previously reported data on BaNd2O4and BaSm2O4corroborate this trend. Missing data for compounds in BaO–Ln2O3(Ln = La, Pr, Eu, Er) systems were estimated from established relations, thermodynamic assessment was performed, and binary phase diagrams were calculated.more » « less
-
Abstract Calcium germanides with two mid‐late rare‐earth metals, Ca5−xGdxGe3and Ca5−xTbxGe3(x≈0.1−0.2), have been synthesized and structurally characterized. Additionally, a lanthanum‐rich germanide with calcium substitutions, La5−xCaxGe3(x≈0.5) has also been identified. The three structures have been established from single‐crystal X‐ray diffraction methods and confirmed to crystallize with the Cr5B3‐type in the tetragonal space groupI4/mcm(no. 140;Z=4; Pearson symboltI32), where part of the germanium atoms are interconnected into Ge2‐dimers, formally [Ge2]6−. Rare‐earth metal and calcium atoms are arranged in distorted trigonal prisms, square‐antiprisms and cubes, centered by Ge or rare‐earth/calcium metal atoms. These studies show that the amount of trivalent rare‐earth metal atoms substituting divalent calcium atoms is in direct correlation with the lengths of the Ge−Ge bond within the Ge2‐dimers, with distance varying between 2.58 Å in Ca5−xGdxGe3and 2.75 Å in La5−xCaxGe3. Such an elongation of the Ge−Ge bond is consistent with the notion that the parent Ca5Ge3Zintl phase (e. g. (Ca2+)5[Ge2]6−[Ge4−]) is being driven out of the ideal valence electron count and further reduced. In this context, this work demonstrates the ability of the germanides with the Cr5B3structure type to accommodate substitutions and wider valence electron count while maintaining their global structural integrity.more » « less
-
Abstract Self‐sustaining photocatalytic NO3−reduction systems could become ideal NO3−removal methods. Developing an efficient, highly active photocatalyst is the key to the photocatalytic reduction of NO3−. In this work, we present the synthesis of Ni2P‐modified Ta3N5(Ni2P/Ta3N5), TaON (Ni2P/TaON), and TiO2(Ni2P/TiO2). Starting with a 2 mM (28 g/mL NO3−−N) aqueous solution of NO3−, as made Ni2P/Ta3N5and Ni2P/TaON display as high as 79% and 61% NO3−conversion under 419 nm light within 12 h, which correspond to reaction rates per gram of 196 μmol g−1 h−1and 153 μmol g−1 h−1, respectively, and apparent quantum yields of 3–4%. Compared to 24% NO3−conversion in Ni2P/TiO2, Ni2P/Ta3N5and Ni2P/TaON exhibit higher activities due to the visible light active semiconductor (SC) substrates Ta3N5and TaON. We also discuss two possible electron migration pathways in Ni2P/semiconductor heterostructures. Our experimental results suggest one dominant electron migration pathway in these materials, namely: Photo‐generated electrons migrate from the semiconductor to co‐catalyst Ni2P, and upshift its Fermi level. The higher Fermi level provides greater driving force and allows NO3−reduction to occur on the Ni2P surface.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D3CE00834G
