Materials Literature
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We perform total energy calculations based on the tight-binding Hamiltonian scheme (i) to study the structural properties and energetics of the extended {311} defects depending upon their dimensions and interstitial concentrations and (ii) to find possible mechanisms of interstitial capture by and release from the {31…
Using coherent anti-Stokes Raman and linear absorption spectroscopy we present experimental evidence for a novel electron trapping mechanism in Sm doped CaF2. The appearance of additional Raman lines after ionization of the Sm2+ ions, their dependence on the Sm3+ concentration and their behavior due to an enhancement…
We will discuss the meaning of piezo-, pyro-, ferro- and antiferroelectricity (defined for solids) and their possible appearance in the liquid state. We will do this using general symmetry principles as a starting point. The arguments will also be used for the prediction of non-linear optical properties in the liquid…
Anelastic relaxations of amorphous Zr65Al7.5Cu27.5 have been studied in the range of the glass transition and in the supercooled liquid. Applying a force step function, an anelastic aftereffect of the form exp(t/τ)β (Kohlrausch–Williams–Watts function) is expected with an exponent β<1. From the measurement a va…
The reorientation of a nearly spherical paramagnetic tracer dissolved in supercooled o-terphenyl is studied by electron spin resonance in the range 200 K < T < 370 K. For T > 300 K the rotational correlation time tau(2) follows the Debye-Stokes-Einstein law. On decreasing the temperature, the rotational motio…
Crystallographic studies on adenylate kinase (AK) suggest that binding of ATP causes the LID domain of the enzyme to close over the ATP molecule (Schlauderer et al. (1996) J. Mol. Biol. 256, 223-227). The method of time-resolved fluorescence resonance energy transfer was applied to study the proposed structural change…
We examine the effect of dipolar interactions on the liquid-crystalline phase behaviour of L/D = 5 hard spherocylinders with a terminal point dipole. The hard spherocylinder consists of a cylinder of length L and diameter D with hemispherical caps on each end; the point dipole is located at the centre of the hemispher…
A complex sequence of ferro- and antiferromagnetic interactions occurs in the compound [Ni(N,N′-dmen)(μ-N3)2] (N,N′-dmen N,N′-dimethylethylenediamine), which exists as a one-dimensional chain in the solid state (shown below; C atoms of the amine ligands are omitted). The magnetic behavior of this unusual spin system…
The effects of an applied magnetic field during anodization on the structural and optical isotropy of luminescent porous silicon (PS) are investigated. The PS layers are prepared by anodizing p-type Si wafers in HF solutions with an external magnetic field of 0–1.7 T applied perpendicular to the Si surface. It is show…
A qualitative description of a spinodal decomposition kinetics is proposed. It is made of a linear stage followed by two nonlinear stages, leading, respectively, to higher and lower frequency generation in the spatial order parameter distribution, then followed by the classical Ostwald ripening. This general scheme is…
A structure reminiscent of the YBa2Cu3O7 superconductor is shown by the novel reduced manganese perovskite YBaMn2O5 (on the right), in which double layers of MnO5 square pyramids enclose the Ba2+ ions (large spheres), while Y3+ ions (medium-sized black spheres) lie between the layers. Unlike many oxidized Mn perovskit…
The highest negative charge of a 16-electron system known to date is shown by the CO2-analogous anion (CBC)5− in Al3BC3. This has been confirmed by the vibrational spectroscopic and structural characterization of this compound, which revealed the linearity and bond lengths given below. Al3BC3 can be regarded as the…
Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure, and temperature distributions for the gas inside a bubble oscillating under an ultrasonic field. The solutions show that sonoluminescence occurs due to the increase and subsequent decrease in bubble wall accelerati…
Under strong nanosecond excitation, we demonstrate that II–VI semiconductor quantum dots exhibit optical gain up to room temperature. The CdS nanocrystallites, fabricated by sol-gel process, are embedded in a sodium borosilicate glass matrix. The gain is spectrally broad and the crossing between absorption and gain is…
Mit elongierten, hexagonal‐prismatischen Keimen beginnt das hierarchische Wachstum anisotroper Kugelaggregate aus Fluorapatit in Gelatine‐Matrices. Durch selbstähnlich verzweigte, nadelförmige Aufwachsungen an den Enden der Keime entstehen diskrete Hantelaggregate (rasterelektronenmikroskopische Aufnahme rechts), die…
The isotropic - nematic (I - N) phase transition in dispersions of sterically stabilized rod-like boehmite (AlOOH) colloids is studied. We have examined the influence of the steric stabilizer, the dispersion medium and the presence of non-adsorbing polymer on the phase transition process. Dispersions in cyclohexane sh…
The rheological properties of colloidal suspensions of spheres and rods have been studied using dissipative particle dynamics (DPD). We have measured the viscosity as a function of shear rate and volume fraction of the suspended particles. The viscosity of a 30 vol% suspension of spheres displays characteristic shear-…
Amorphous Si/SiO2 superlattices with 100–525 periods and a 2–3 nm periodicity were deposited by radio frequency magnetron sputtering onto silicon and quartz substrates. All samples exhibited visible photoluminescence (PL) at room temperature and the PL peak wavelength shifted towards shorter wavelengths with decreasin…
We report Monte Carlo simulations that show both vapor-liquid and closed-loop liquid-liquid equilibrium in a pure substance, for a model fluid that forms orientation-dependent intermolecular bonds. This is the first time that direct evidence of liquid-liquid immiscibility in a pure fluid has been found using exact met…
One of the most serious forms of damage that occurs during the integration of Pt/PZT/Pt ferroelectric capacitors [where PZT is Pb(ZrxTi1−x)O3] is the disappearance of polarization hysteresis characteristics during the passivation process. The hydrogen content of the atmosphere during this process affects the ferroelec…