Materials Literature
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Branching out: Stiff, aromatic dendrimers made up of five and seventeen pyrene units, respectively, are synthesized, characterized, and compared with two model compounds. The rigid and strongly twisted structure allows a precise spatial arrangement in which each unit is a chromophore. The high extinction coefficients…
We formulate a theoretical model of the shear failure of a thin film tethered to a rigid substrate. The interface between film and substrate is modeled as a cohesive layer with randomly fluctuating shear strength/fracture energy. We demonstrate that, on scales large compared with the film thickness, the internal shear…
We propose a superlens formed by an ultradense array of crossed metallic wires. It is demonstrated that, due to the anomalous interaction between crossed wires, the structured substrate is characterized by an anomalously high index of refraction and supports strongly confined guided modes with very short propagation w…
We use first-principles density functional theory (DFT) calculations to investigate the ground-state structures of PbTiO(3) solid solutions containing Ni, Pd, and Pt. Anomalous effective charges are reported, including the first report of negative Born effective charges for nominal +2 cations. We predict that these pr…
The interaction of cobalt atoms with silicon (111) surface has been investigated by means of scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Besides the Co silicide islands, we have successfully distinguished two inequivalent Co-induced $\sqrt{13}\times\sqrt{13}$ reconstructions on Si (…
A simple and most promising oxide-assisted catalyst-free method is used to prepare silicon nitride nanowires that give rise to high yield in a short time. After a brief analysis of the state of the art, we reveal the crucial role played by the oxygen partial pressure: when oxygen partial pressure is slightly below the…
The synthesis of Si3N4 nanowires from the reaction of silicon nanoparticles with N2 in the 1200-1440 C temperature range is reported. The nitridation conditions are such that the reaction with nitrogen is favoured by the presence of silicon oxide in the particles and by the active oxidation of silicon without a cataly…
The modulation of charge density and spin order in ${({\text{LaMnO}}_{3})}_{2n}/{({\text{SrMnO}}_{3})}_{n}$ $(n=1--4)$ superlattices is studied via Monte Carlo simulations of the double-exchange model. $G$-type antiferromagnetic barriers in the ${\text{SrMnO}}_{3}$ regions with low charge density are found to separate…
According to the recent experiment by the Fert group, the velocity of domain wall motion in the spin valve ferromagnetic nanowires was almost doubly enhanced compared to the old value. In this work, we propose an additional torque model, arising from the interlayer exchange interaction, which can enhance or suppress t…
We report preparation of stimuli-responsive bicomponent polymeric Janus particles and investigation of their switching behavior. The first polymer was immobilized on one side of silica particles using the surface-initiated atom transfer radical polymerization, “grafting from” approach. The second polymer was immobiliz…
Time-dependent density functional theory calculations at the SAOP/TZP level of theory are employed to study the optical absorption spectra of pure metal nanoparticles (Au 25 (SH) 18 − and Ag 25 (SH) 18 − ) and mixed metal “core-shell” systems (Au 13 Ag 12 (SH) 18 − and Ag 13 Au 12 (SH) 18 − ). All four systems exhibit…
Acid trip: A general scale that compares the acidities of metal oxides and sulfides quantitatively is presented, along with Sanderson's electronegativity values of lanthanides.
Plant fibers such as linen are remarkably stiff materials in the longitudinal direction of the fiber. As plant cell walls are composites made of cellulose nanocrystals, the so-called microfibrils, embedded in a disordered matrix, those nanocrystals should exhibit an even higher elastic modulus G . We have determined t…
Silver(I) hexacyanocobaltate(III), Ag(3)[Co(CN)(6)], shows a large negative linear compressibility (NLC, linear expansion under hydrostatic pressure) at ambient temperature at all pressures up to our experimental limit of 7.65(2) GPa. This behavior is qualitatively unaffected by a transition at 0.19 GPa to a new phase…
We present detailed measurements of the longitudinal resistivity ${\ensuremath{\rho}}_{xx}(T,H)$ and the upper critical field ${H}_{c2}$ of ${\text{NdFeAsO}}_{0.7}{\text{F}}_{0.3}$ single crystals in strong dc and pulsed magnetic fields up to 45 and 60 T, respectively. We found that the field scale of ${H}_{c2}$ is co…
The structural and dielectric properties of (1− x )BaTiO 3 – x BiScO 3 ( x =0–0.5) ceramics were investigated to acquire a better understanding of the binary system, including determination of the symmetry of the phases, the associated dielectric properties, and the differences in the roles of Bi 2 O 3 and BiScO 3 sub…
Invisibility and negative refraction are both applications of transformation optics where the material of a device performs a coordinate transformation for electromagnetic fields. The device creates the illusion that light propagates through empty flat space, whereas in physical space, light is bent around a hidden in…
We experimentally demonstrate planar lenses based on nanoscale slit arrays in a metallic film. Our lens structures consist of optically thick gold films with micron-size arrays of closely spaced, nanoscale slits of varying widths milled using a focused ion beam. We find excellent agreement between electromagnetic simu…
Abstract We present theoretical analysis of bromine adsorption on the Ge(001)-p(1×2) surface. Bromine adsorbs dissociatively at the Ge(001) surface and the adlayer of bromine develops ordered structures of adatoms bound to substrate dimers. We analyse atomic configurations of the Ge(001) surface covered by 0.25, 0.5,…
Merck has developed a range of reactive liquid crystal materials (Reactive Mesogens) that are designed to form thin, birefringent, coatable films for optical applications. Reactive Mesogen (RM) films are typically coated from solution and polymerized in-situ to form thin, optics-grade coatings. Merck RM materials are…