Materials Literature
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We have extended the exploration of microscopic dynamics of supercooled liquids to small wave numbers Q corresponding to the scale of intermediate range order, by developing a new experimental approach for precise data correction for multiple scattering noise in inelastic coherent neutron scattering. Our results in su…
In a struggle between unmatched enantiomers to control the helical sense of a polymer, temperature determines the ratio of the chiral competitors at which the right- and left-handed helical senses are equally populated. Deviation above or below this temperature is detected by the optical activity, which then increases…
A new NLO standard has been set by compound 1 for the substance class of analines: Their second-order polarizability β is two orders of magnitude higher than that of the one-dimensional NLO prototype p-nitroaniline. This is an example of the optimization of nonlinear optical chromophores with a threefold axis of symme…
The total structure factor $S(Q)$ and the radial distribution function $G(r)$ of liquid ${\mathrm{Y}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$ (YAG) were measured at 1770--2230 K by x-ray scattering from samples under containerless conditions in Ar and ${\mathrm{O}}_{2}$. Nominal coordination numbers are 4 for ${\mathrm…
We have investigated the electronic structure of Ti3SiC2 by means of first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method. Our calculated volume is in good agreement (within 4%) with experiment. Also, the calculated…
Monodisperse, stabförmige Moleküle 1 aus sich wiederholenden separaten Chromophoreinheiten, die im Grundzustand erheblich miteinander wechselwirken, wurden durch meso-meso-Kupplung von Porphyrinen synthetisiert. Das 128-mer (n=126) ist mit einer Länge von ca. 106 nm das längste derartige System. Die S1-Zustände sind ü…
Structural and dielectric evidences are advanced to show that the ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{TiO}}_{3}$ (SCT) system undergoes an antiferroelectric (AFE) phase transition in the composition range $0.18\ensuremath{\le}x\ensuremath{\le}0.40$. Stabilization of the AFE phase, instead of the…
The cyclic hexamer obtained by the condensation of furan and acetone can be used as a convenient starting material for the syntheses of calix[6]pyrrole 1 and of several “hybrid systems” containing both furan and pyrrole units. The solid-state structure of 1 shows a water molecule held inside the cavity by six hydrogen…
Efforts have been made to characterize the mechanical properties of carbon nanotubes. Previous work has concentrated on the tubes' longitudinal properties, and studies of their radial properties have lagged behind. We have used a scanning probe microscope with an indentation/scratch function to investigate the radial…
A model for the transport of nitrogen in austenitic stainless steel at temperatures around 400 °C is presented and discussed. The model considers the diffusion of nitrogen under the influence of trapping and detrapping at trap sites formed by local chromium. Nitrogen depth profiles simulated on the basis of the model…
The underlying physical phenomena behind the increased reflection/diffraction efficiency of holographically formed polymer-dispersed liquid crystal gratings formed from blended oligomers are investigated. Using parameters determined by in situ diffraction measurements during grating formation, a phenomenological diffu…
Optical conductivity data of the intermetallic compounds $({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{V}}_{x}{)}_{3}\mathrm{Al}$ ( $0\ensuremath{\le}x\ensuremath{\le}0.33$) reveal that their density of states around the Fermi energy ( ${E}_{F}$) is strongly reduced as $x$ is increased. In particular, ${\mathrm{Fe}}_{2}\…
The two-orbital model for manganites with both noncooperative and cooperative Jahn-Teller phonons is studied at hole density x = 0.5 using Monte Carlo techniques. The phase diagram is obtained by varying the electron-phonon coupling and the t(2g)-spins exchange. The insulating CE-type charge- and orbital-ordered state…
A thermodynamic theory is developed for dense laminar domain structures in epitaxial ferroelectric films. It is found that, at some critical misfit strain between the film and substrate, the 90 degrees c/a/c/a domain structure becomes unstable with respect to the appearance of the polarization component parallel to do…
We suceeded in the preparation of polycrystalline Ca_2FeReO_6 which has a Curie temperature of 540 K, the highest value of all magnetic perovskites investigated up to now. This material has been characterised by X-ray and neutron powder diffraction. We found at 548 K a monoclinic unit cell (space group P2_1/n) with a=…
The elaboration of solids from the molecular scale by a kinetically controlled methodology is one of the main challenges of molecular chemistry. In the long term, this should permit the design of solids with desired properties. Here, some examples are given which show a few methods that have been used for the preparat…
Monodisperse, rodlike molecules 1 composed of repeating individual chromophores that have substantial electronic interactions in the ground state have been synthesized by the meso – meso coupling of porphyrins. The 128-mer (n=63) at about 106 nm long is the longest such system known. The S1 states are delocalized over…
We report that calculating the Gibbs free energy of the alpha-Al2O3 (0001) surfaces in equilibrium with a realistic environment containing both oxygen and hydrogen species is essential for obtaining theoretical predictions consistent with experimental observations. Using density-functional theory we find that even und…
We construct the 1/S spin-wave expansion for double exchange ferromagnets at T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently large, resulting in a fully saturated, ferromagnetic half-metallic ground state. We evaluate corrections to the magnon dispersion law, and we also find that, in c…
Using Brownian molecular dynamics simulation, we study the surface dynamics near the reconstruction transition of W(100) via a model Hamiltonian. Results for the softening and broadening of the surface phonon spectrum near the transition are compared with previous calculations and with He atom scattering data. From th…