Materials Literature
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We report new zero-field muon spin relaxation and neutron spin echo measurements in ferromagnetic (FM) (La,Ca)MnO3 which suggest at least two spatially separated regions possessing very different Mn-ion spin dynamics. One region displays diffusive relaxation, "critical slowing down" near T(C) and an increasing volume…
We have studied ultraviolet photoluminescence from high-purity zinc-oxide powder over a wide temperature range (2–293 K). At low temperatures, the spontaneous emission is due to radiative recombination of excitons bound to donors and acceptors. At high temperature (>90 K), it mainly consists of recombination of…
Experimental evidence has been found for the existence of small single wall carbon nanotubes with diameters of 0.5 and 0.33 nm by high resolution transmission electron microscopy, and their mechanical stability was investigated using tight-binding molecular dynamics simulations. It is shown that, while the carbon tube…
(Ga,Mn)As digital ferromagnetic heterostructures are grown by incorporating submonolayer planes of MnAs into GaAs using molecular beam epitaxy. Structural and magnetic measurements indicate single-crystalline superlattice structure and ferromagnetic order with Curie temperatures (TC) up to 50 K. By varying the spacing…
The Born effective charge, Z *, that describes the polarization created by collective atomic displacements, can be computed from first principles following different techniques. We establish the connections existing between these different formulations, and analyse the related band-by-band decompositions. We show that…
A simple model was constructed to describe the polar ordering of non-centrosymmetric supramolecular aggregates formed by self assembling triblock rodcoil polymers. The aggregates are modeled as dipoles in a lattice with an Ising-like penalty associated with reversing the orientation of nearest neighbor dipoles. The ch…
We suggest a ``ping-pong'' mechanism of enhancement for fusion reactions between a low energy external deuteron beam and the deuterons in a condensed matter or molecular target. The mechanism is based on the possibility of acceleration of a target deuteron by the Coulomb field of a projectile deuteron with its subsequ…
We propose a time-dependent boundary condition coupling an atomistic simulation system to linear surroundings such that reflection of elastic waves across the boundary is minimized. Interdomain interactions expressed in terms of memory kernel functions within linear-response theory are treated in a natural dynamical m…
Experimental results for single-bubble sonoluminescence of air bubbles at very low frequency f = 7.1 kHz are presented: In contrast to the predictions of a recent model [S. Hilgenfeldt and D. Lohse, Phys. Rev. Lett. 82, 1036 (1999)], the bubbles are only as bright (10(4)-10(5) photons per pulse) and the pulses as long…
Properties such as the glass transition temperature ( T(g)) and the diffusion coefficient of ultrathin polymeric films are shown to depend on the dimensions of the system. In this work, a hard-sphere molecular dynamics methodology has been applied to simulate such systems. We investigate the influence that substrates…
We find a correlation between the dynamics of fluorescence intermittency and spectral diffusion in the spectroscopy of single CdSe nanocrystal quantum dots (QD). A statistical analysis of the data suggests two populations of blinking events: blinking followed by large spectral diffusion shifts and blinking with small…
Electrochemical characteristics of supercapacitors built from multiwalled carbon nanotubes electrodes have been investigated and correlated with microtexture and elemental composition of the materials. Capacitance has been estimated by cyclovoltammetry at different scan rates from 1 to 10 mV/s, galvanostatic discharge…
This contribution presents a systematic light scattering study of a series of boron oxide glasses which are characterized by different thermal histories. The thermal treatment was obtained by annealing the samples close to the glass transition temperature for times of several hours. Both low-frequency (0.1–30 cm−1) an…
We study the phase behavior of the Zwanzig model of suspensions of hard rods, allowing for polydispersity in the lengths of the rods. In spite of the simplified nature of the model (rods are restricted to lie along one of three orthogonal axes), the results agree qualitatively with experimental observations: the coexi…
Some new analytic results concerning the foam drainage equation are described. The temporal approach to the equilibrium profile of the foam is shown to be exponential, in agreement with numerical calculations. The effect of including the equilibrium distribution of the liquid fraction as an initial condition is discus…
The polymerization of solid acetylene under pressure has been studied by Fourier transform infrared (FTIR) spectroscopy. Controlled laser irradiation cycles and the employment of infrared sensors to measure the sample pressure, allowed to separate the photochemical and the pressure effect on the injection and on the e…
We have investigated with extensive Monte Carlo simulations in the isothermal isobaric ensemble a system of N=8192 elongated attractive-repulsive biaxial Gay–Berne (GB) particles. We have found uniaxial and biaxial nematic phases and a biaxial orthogonal smectic phase in this thermotropic model system.
Diffusion of a particle in the N-dimensional external potential which is periodic in one dimension and unbounded in the other N-1 dimensions is investigated. We find an analytical expression for the overdamped diffusion and study numerically the cases of moderate and low damping. We show that in the underdamped limit,…
The criteria for the existence of supersonic and multiple topological excitations (kinks) in the driven Frenkel-Kontorova model (a chain of atoms placed into an external periodic potential) with anharmonic (exponential) interatomic interactions are studied.
Geometric structures of three types of supramolecular aggregates composed of bis(phthalocyaninato)lutetium (Lu(Pc) 2 ) radicals are investigated by means of ESR measurements and theoretical calculations. The tetra-crown-substituted complex, Lu(CR 4 Pc)(Pc) (CR 4 Pc = tetra-15-crown-5 substituted Pc), forms an aggregat…