A basis theorem for the degenerate affine oriented Brauer-Clifford supercategory

We introduce the oriented Brauer-Clifford and degenerate affine oriented Brauer-Clifford supercategories. These are diagrammatically defined monoidal supercategories which provide combinatorial models for certain natural monoidal supercategories of supermodules and endosuperfunctors, respectively, for the Lie superalgebras of type Q. Our main results are basis theorems for these diagram supercategories. We also discuss connections and applications to the representation theory of the Lie superalgebra of type Q.Comment: 37 pages, many figures. Version 3 replaces the partial results from the previous versions with a proof by the first author of a basis theorem for cyclotomic quotients at all levels. Various other minor corrections and revisions were mad

Generarized Cubic Model for BaTiO3_3-like Ferroelectric Substance

We propose an order-disorder type microscopic model for BaTiO$_3$-like Ferroelectric Substance. Our model has three phase transitions and four phases. The symmetry and directions of the polarizations of the ordered phases agree with the experimental results of BaTiO$_3$. The intermediate phases in our model are known as an incompletely ordered phase, which appears in a generalized clock model.Comment: 6 pages, 4figure

Neutron and x-ray diffuse scattering study of tetrathiofulvalene tetracyanoquinodimethane (TTF--TCNQ)

Results of extensive x-ray and neutron scattering experiments are: (1) Below the Peierls transition taking place at 54/sup 0/K, two additional structural phase transitions are observed at 49/sup 0/K and 38/sup 0/K. (2) Above the Peierls transition two different precursor 1-d fluctuations have been observed. Suggestions for future studies are given. (LK

Click Chemistry for the Assembly of Gold Nanorods and Silver Nanoparticles

The synthesis of compact nanostructures with highly integratedfunctionalities through the controlled assembly ofnanoparticles (NPs) is potentially of broad interest in researchfields such as drug delivery, multimodal imaging, andelectronic devices. This concept seems to be particularlyimportant in view of the emerging concept of theranostic,according to which both therapeutic and diagnostic capabilitiescan be present in two nanostructures. A key step, however,is how to combine individual nanostructures withoutloosing the original properties

Band-Engineered LaFeO3_{3}-LaNiO3_{3} Thin Film Interfaces for Electrocatalysis of Water

Transition metal oxides have generated significant interest for their potential as catalysts for the oxygen evolution reaction (OER) in alkaline environments. Iron and nickel-based perovskite oxides have proven particularly promising, with catalytic over-potentials rivaling precious metal catalysts when the alignment of the valence band relative to the OER reaction potential is tuned through substitutional doping or alloying. Here we report that engineering of band alignment in LaFeO$_{3}$/LaNiO$_{3}$ (LFO/LNO) heterostructures via interfacial doping yields greatly enhanced catalytic performance. Using density functional theory modeling, we predict a 0.2 eV valence band offset (VBO) between metallic LNO and semiconducting LFO that significantly lowers the barrier for hole transport through LFO compared to the intrinsic material and make LFO a p-type semiconductor. Experimental band alignment measurements using in situ X-ray photoelectron spectroscopy of epitaxial LFO/LNO heterostructures agree quite well with these predictions, producing a measured VBO of 0.3(1) eV. OER catalytic measurements on the same samples in alkaline solution show an increase in catalytic current density by a factor of ~275 compared to LFO grown on n-type Nb-doped SrTiO$_{3}$. These results demonstrate the power of tuning band alignments through interfacial band engineering for improved catalyticComment: 13 pages, 5 figures; Supplemental info: 5 pages, 5 figure

Glitz

The crystal structure of the orthorhombic and tetragonal phases of La(Ba 2-xLax)Cu3-yO 6+x/2-y+ z are determined on twinned crystals. The orthorhombic structure, obtained for low x, is close to the regular Y-Ba-Cu-O type (twin a * b * c-b * a * c), but is highly copper deficient on the Cu(1) site (~ 30 %). The local correlations (ξ ~ 20 Å) between copper atoms and vacancies, as deduced from X-ray diffuse scattering, correspond to a short-range segregation of vacancies in chains. As a consequence of the large amount of defects, these crystals are non-typical semiconductors. The tetragonal structure, x ≃ 0.50, leads to tri-twinned crystals with 90° faulting, a * a * 3 a-a * 3 a * a -3 a * a * a (a, the perovskite lattice constant). In these materials the copper sites are found to be strongly anharmonic. This is due to the disorder introduced by the La-Ba substitution. These crystals are also semiconductors with a T-1/4 activation law for the conductivity which indicates that variable range hopping is expected to set in, a consequence of localization by the disorder

Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO3_{3} Thin Films

Transition metal oxides have long been an area of interest for water electrocatalysis through the oxygen evolution and oxygen reduction reactions. Iron oxides, such as LaFeO$_{3}$, are particularly promising due to the favorable energy alignment of the valence and conduction bands comprised of Fe$^{3+}$ cations and the visible light band gap of such materials. In this work, we examine the role of band alignment on the electrocatalytic oxygen evolution reaction (OER) in the intrinsic semiconductor LaFeO$_{3}$ by growing epitaxial films of varying thicknesses on Nb-doped SrTiO$_{3}$. Using cyclic voltammetry and electrochemical impedance spectroscopy, we find that there is a strong thickness dependence on the efficiency of electrocatalysis for OER. These measurements are understood based on interfacial band alignment in the system as confirmed by layer-resolved electron energy loss spectroscopy and electrochemical Mott-Schottky measurements. Our results demonstrate the importance of band engineering for the rational design of thin film electrocatalysts for renewable energy sources.Comment: 19 pages, 6 figures; authors Burton and Paudel contributed equally; supplement: 11 pages, 7 figure