Materials Literature
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Molecular dynamics simulation is used to reveal the origin of increased molecular mobility that accompanies plastic deformation of a glassy amorphous polymer under an applied stress. Significant increases in torsional transition rates are observed during active deformation prior to and just beyond the yield point. The…
Heterocyclic π-electron polymers such as polythiophene, polypyrrole, and polyfuran attract wide interest on both experimental and theoretical levels. While the optical properties of these materials are dominated by the band gap, no accurate, reliable computational method currently exists to predict the band gaps of la…
A phenomenological theory of magnetic and magnetoelectric (ME) susceptibilities of ferroelectric/ferromagnetic composites is presented and applied to the special case of layered structures. Expressions have been obtained relating the magnetic and ME susceptibility tensor components of the composite (symmetry point gro…
In this paper we develop a technique for determining interatomic potentials in materials in the quantum regime from single--shell Extended X-ray Absorption Spectroscopy (EXAFS) spectra. We introduce a pair distribution function, based on ordinary quantum time--independent perturbation theory. In the proposed scheme, t…
We present a numerical model study of the zero-temperature infrared optical properties of (III,Mn)V diluted magnetic semiconductors. Our calculations demonstrate the importance of treating disorder and interaction effects simultaneously in modelling these materials. We find that the conductivity has no clear Drude pea…
We have carried out an ultrahigh-field cyclotron resonance study of n-type ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ films, with Mn composition x ranging from 0% to 12%, grown on GaAs by low-temperature molecular-beam epitaxy. We observe that the electron cyclotron resonance peak shifts to lower f…
A type of metal-dielectric composites has been proposed that is characterized by a resonancelike behavior of the effective permeability ${\ensuremath{\mu}}_{\mathrm{eff}}$ in the infrared and visible spectral ranges. This material can be referred to as an optomagnetic medium. It consists of conducting inclusions in th…
The physics of a two-level system coupled to Ohmic bath is studied by means of the perturbation approach based on a unitary transformation. Our main results are: The coherence-incoherence transition is at $α_c={1\over 2}[1+Δ_r/ω_c]$; for $α<α_c$ the dynamical quantity $P(t)=\cos(ω_0 t)\exp(-γt)$; the sussceptibility $…
It has been observed that the effect of magnetic impurities in a superconductor is drastically different depending on whether the host superconductor is in a crystalline or an amorphous state. Based on the recent theory of Kim and Overhauser (KO), it is shown that as the system is getting disordered, the initial slope…
The stability of ${\mathrm{M}\mathrm{g}\mathrm{H}}_{2}$ has been studied up to 20 GPa using density-functional total-energy calculations. At ambient pressure $\ensuremath{\alpha}\mathrm{\text{\ensuremath{-}}}{\mathrm{M}\mathrm{g}\mathrm{H}}_{2}$ takes a ${\mathrm{T}\mathrm{i}\mathrm{O}}_{2}$-rutile-type structure. $\e…
We performed density-functional theory calculations in the local-density approximation of the structural, electronic, and optical properties of 4-$\mathrm{\AA{}}$-diameter single-walled carbon nanotubes. The calculated relaxed geometries show significant deviations from the ideal rolled graphene sheet configuration. W…
A theoretical investigation of the angular distributions of photoelectrons (ADP) ejected from fixed-in-space molecules or clusters having C2v symmetry is presented. The consideration is based on an expansion of the photoelectron wave functions in symmetry-adapted spherical harmonics. The ADP is derived for linearly po…
Two strong violet-blue luminescence emissions at 390 and 440 nm under excitation at room temperature have been observed in the ordered mesoporous zirconium oxide post-treated with phosphoric acid. The oxide was characterized by powder x-ray diffraction, nitrogen adsorption, diffuse reflectance UV-vis spectroscopy, x-r…
Nematic emulsions and polymer dispersed liquid crystals (PDLCs) are composite materials formed by micron-sized droplets of mesogenic molecules, which are embedded in fluid or solid matrices, respectively. Both systems can be switched from an opaque to a trasparent state by application of a suitable electric field. The…
The mean field theory proposed originally by Kubo and Ohata for manganites is generalized for a ferrimagnetic half-metal and applied to the magnetite. The relevance of both the double exchange interaction and the superexchange one for the spin ordering in the conducting B sublattice of magnetite is shown. The shortcom…
The phase behavior of a liquid-crystal forming model colloidal system containing hard rodlike and platelike particles is studied using the Parsons–Lee scaling [J. D. Parsons, Phys. Rev. A 19, 1225 (1979); S. D. Lee, J. Chem. Phys. 87, 4972 (1987)] of the Onsager theory. The rod and plate molecules are both modeled as…
The adsorption of hydrogen (deuterium) and oxygen on neutral platinum clusters has been investigated in a cluster beam experiment. The beam passes through two low-pressure reaction cells and the clusters, with and without adsorbed molecules, are detected by laser ionization and mass spectrometry. Both H2 and O2 adsorb…
In this letter, magnetization reversal is investigated in (Ga,Mn)As thin films using the magneto-optical Kerr effect. A Stoner–Wohlfart model, modified to take into account the existence of magnetic reversal discontinuities associated with nucleation and propagation phenomena allows us to estimate most of the characte…
The population change of the photoluminescence (PL) W center (or ${I}_{I}$ center) with 2-MeV electron irradiation in proton-implanted silicon crystal was observed to investigate the origin of the center. While a straightforward annihilation of the W centers formed by proton implantation with an increase of the electr…
The bonding of atomic oxygen to ferrous iron was studied using the Fe(OH)2 system as a model of the ferrous iron center. All lowest triple, quintet, and septet states of OFe(OH)2 were studied at the complete active-space self-consistent-field theory level augmented by multireference second-order-perturbation theory. I…