On a Thomas-Fermi model of "hollow" atom
A Thomas-Fermi model of a spherical shell of positive charge is investigated, under various boundary conditions. The electron distribution and the ionization charge are given particular attention.
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First Step Towards Planning of Syntheses in Solid‐State Chemistry: Determination of Promising Structure Candidates by Global Optimization
Abstract A method is presented here that allows, in principle, the prediction of the existence and structure of (meta)stable solid compounds. It is based on a set of adjustable modules that are applied to the study of the energy function of the chemical system of interest. The main elements are a set of routines for g…
Growth, transport, and magnetic properties of Pr0.67Ca0.33MnO3 thin films
We have grown Pr0.67Ca0.33MnO3 thin films on LaAlO3 using pulsed laser deposition. Below 50 K, a field induced insulator-metal transition results in changes in resistivity of at least 6 orders of magnitude. The field induced conducting state is metastable at low temperature. The temperature dependence of the resistivi…
Effect of Chiral Domain Walls on the Specific Heat of Gd(hfac)3NITR(R=Ethyl, Isopropyl, Methyl, Phenyl) Molecular Magnetic Chains
We measured the thermodynamic properties for a class of quasi-one-dimensional (1D) molecular magnets with alternating spins and competing nearest- and next-nearest-neighbor exchange interactions. For the two compounds with higher frustration ( $R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{ethyl}$ and $R…
Sol–gel phase transitions in thermoreversible gels: Onset of gelation and melting
A Monte Carlo simulation model is proposed to study the phase transition and the structural evolution of thermoreversible gels with the coexistence of phase separation and gelation processes. Our model includes the mobility of all the species and the reversibility of bonds of the clusters formed due to cross-linking r…
Plasma beam deposited amorphous hydrogenated carbon: Improved film quality at higher growth rate
High quality diamondlike a-C:H has been deposited, at low ion bombardment energies, from an expanding thermal argon/acetylene plasma at high growth rate. It is observed that quality improvement, in terms of hardness, is equivalent to maximization of the refractive index. The highest refractive indices are obtained whe…
Inelastic neutron scattering study of low energy excitations in glassy 1-butene
Glassy 1-butene (CH2=CHCH2CH3) was studied by incoherent inelastic neutron scattering below 10 meV in the temperature range 18≤T≤80 K covering the glass transition temperature (Tg=60 K). A broad excitation peak due to the low-energy excitation was found at 3–4 meV. The spectra corrected for the Bose factor could be sc…
Response theory for static and dynamic polarizabilities of excited states
We demonstrate a fully analytical method for calculations of excited state static and dynamic polarizabilities. From the double residues of a single reference state cubic response function all excited state polarizabilities can be determined. The method forms also a basis for calculations of excited state hyperpolariz…
Bulk Superconductivity at 10 K in the Layered CompoundsY2C2I2andY2C2Br2
Resistivity, susceptibility, and specific heat measurements on the new layered superconductors ${\mathrm{Y}}_{2}{\mathrm{C}}_{2}{\mathrm{I}}_{2}$ and ${\mathrm{Y}}_{2}{\mathrm{C}}_{2}{\mathrm{Br}}_{2}$ have been performed to characterize their superconducting state. Our experiments indicate bulk superconductivity with…
Combined magnetron sputtering and pulsed laser deposition of carbides and diamond-like carbon films
A hybrid technique is reported, which combines magnetron sputtering and pulsed laser ablation to produce plasma fluxes intersected on a substrate surface to form metal, ceramic and diamond-like materials. Deposition of crystalline Ti, TixCy, TiCN, and amorphous diamond-like carbon films at low temperatures by the new…
Liquid-Crystalline Phases of Semiflexible Diblock Copolymer Melts
Self-consistent field theory is used to study the phase behavior of melts of semiflexible diblock copolymers. Repulsion between the incompatible blocks leads to microphase separation, while anisotropic external fields and interactions between polymers induce liquid-crystalline phases. Considering symmetric diblocks wi…
Synthesis of carbon nanotubes from bulk polymer
Carbon nanotubes have been synthesized by heat treating the polymer at 400 °C in air which was obtained by polyesterification between citric acid and ethylene glycol. Transmission electron micrographs and an electron diffraction pattern showed the formation of carbon nanotubes. The diameter of the tubes ranged from 5…
Pressure-Induced Crossover from Long- to Short-Range Order in Compositionally Disordered Soft Mode Ferroelectrics
Results on a lanthanum-modified, lead zirconate-titanate have revealed (1) pressure-induced crossover from normal ferroelectric- (nFE-) to-relaxor (R) behavior; (2) the continuous evolution of the dynamics of the relaxation process; (3) a spontaneous R-to-nFE transition at a temperature well below the dynamic glass te…
Polyamorphism and density anomalies in network-forming fluids: Zeroth- and first-order approximations
A molecular model of network-forming liquids has been formulated in terms of a lattice fluid in which bond formation depends strongly on molecular orientations and local density. The model has been solved in the zeroth- and first-order approximations for molecular and bond geometries similar to water or silica. Result…
Fast Dynamics of Glass-Forming Glycerol Studied by Dielectric Spectroscopy
Dielectric spectroscopy up to 370 GHz has been performed on supercooled glycerol for temperatures between 250 and 330 K. The high-frequency dielectric loss, ${\ensuremath{\varepsilon}}^{\ensuremath{'}\ensuremath{'}}$, has been investigated by coherent-source submillimeter-wave spectroscopy. Special attention is given…
Deviations from Drude Response in Low-Dimensional Metals: Electrodynamics of the Metallic State of (TMTSF)2PF6
The optical properties of the linear chain compound bis-(tetramethyltetraselenafulvalene)hexafluoro-phosphate, (TMTSF${)}_{2}$P${\mathrm{F}}_{6}$, were examined in an extremely wide frequency range in the metallic state, above the spin density wave transition ( $T>12\mathrm{K}$). Parallel to the chains the conducti…
Monte Carlo simulations of the recombination dynamics in porous silicon
A simple lattice model describing the recombination dynamics in visible-light-emitting porous silicon is presented. In the model, each occupied lattice site represents a Si crystal of nanometre size. The disordered structure of porous silicon is modelled by modified random percolation networks in two and three dimensi…
Defect and transport properties of nanocrystalline CeO2−x
It is shown that unique defect thermodynamics and transport properties result for oxides of a few nanometers crystallite size. Fully-dense CeO2−x polycrystals of ∼10 nm grain size were synthesized, and their electrical properties compared with those of samples coarsened from the same material. The nanocrystals showed…
Raman shifts in Si nanocrystals
Raman shifts of Si nanocrystals versus size were studied theoretically by a bond polarizability model. Zero-dimensional spheres and one-dimensional columns were considered. The relation between the Raman shift and the size for Si spheres and columns was established, from which the size of Si nanocrystals can be obtain…
Surface Spin Disorder in NiFe 2 O 4 Nanoparticles
Nickel ferrite nanoparticles exhibit anomalous magnetic properties at low temperatures: low magnetization with a large differential susceptibility at high fields, hysteresis loops which are open up to 160 kOe, time-dependent magnetization in 70 kOe applied field, and shifted hysteresis loops after field cooling. We pr…