Materials Literature
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We present a phenomenological force-constant model developed for the description of lattice dynamics of $s{p}^{2}$ hybridized carbon networks. Within this model approach, we introduce a set of parameters to calculate the phonon dispersion of graphene by fitting the ab initio dispersion. Vibrational modes of carbon nan…
Simultaneous measurement of self-diffusion of iron and nitrogen in amorphous iron nitride (Fe86N14) using secondary ion mass spectroscopy (SIMS) technique has been done. In addition neutron reflectivity (NR) technique was employed to study the Fe diffusion in the same compound. The broadening of a tracer layer of 57Fe…
A generic Fourier-space approach to solve the self-consistent field theory of block copolymers is developed. This approach is based on the fact that, for any computational box with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the bo…
Using a combination of quantum and classical computational approaches, we model the electronic structure in amorphous silicon in order gain understanding of the microscopic atomic configurations responsible for light induced degradation of solar cells. We demonstrate that regions of strained silicon bonds could be as…
Raman spectroscopic investigations are carried out on ZnO nanoparticles for various photon energies. Intensities of E1-LO and E2 modes exhibit large changes as the excitation energy varied from 2.41 to 3.815 eV, signifying substantially large contribution of Frohlich interaction to the Raman polarizability as compared…
The effects of correlation-induced coupling between spin and charge fluctuations on spin-wave excitations in a band ferromagnet are investigated by including self-energy and vertex corrections within a systematic inverse-degeneracy expansion scheme which explicitly preserves the Goldstone mode. Arising from the scatte…
Hexagonal $h$-BN/metal interfaces for different $3d$, $4d$, and $5d$ metals are studied in terms of ab initio density functional theory. The trends across the periodic table of the bonding of $h$-BN to the metal surfaces are discussed. We show that the binding energy between $h$-BN and the metal surface decreases with…
We report first principles calculations of the phonon dispersions of PbTe both for its observed structure and under compression. At the experimental lattice parameter we find a near instability of the optic branch at the zone center, in accord with experimental observations.This hardens quickly towards the zone bounda…
We present a model system that might serve as a blueprint for the controlled layout of graphene based nanodevices. The systems consists of chains of B(7) clusters implanted in a graphene matrix, where the boron clusters are not directly connected. We show that the graphene matrix easily accepts these alternating B(7)-…
By Monte Carlo simulations in the canonical ensemble, we have studied the magnetic anisotropy in Fe/Dy amorphous multilayers. This work has been motivated by experimental results which show a clear correlation between the magnetic perpendicular anisotropy and the substrate temperature during elaboration of the samples…
We studied exchange bias in magnetic multilayers incorporating antiferromagent CoO doped with up to 35 atomic percent of Pt. The exchange bias increased with doping in epitaxial films, but did not significantly change in polycrystalline films at the lowest measured temperature of 5 K, and decreased at higher temperatu…
We have developed a method to simulate behavior of nanoporous materials in a molecular dynamics code. The nanoporous solid is produced via a spinodal decomposition of a material brought from a supercritical fluid into the two phase (liquid-vapor) region and then quenching and freezing the liquid into an interconnected…
In the early days of high temperature superconductivity it was already recognized that magnetic properties of these materials are intimately related to the superconducting ones . When doped, the long-range ordered antiferromagnetic background of pristine copper-oxide insulators melts away and makes room for a spin liq…
We have performed zero-field $^{75}$As nuclear magnetic resonance study of SmFeAsO$_{1-x}$F$_x$ (x=0, 0.07) polycrystals in a wide frequency range at various temperatures. $^{75}$As resonance line was found at around 265 MHz revealing the formation of the intermetallic FeAs clusters in the new layered superconductors.…
A low temperature micro solid oxide fuel cell with corrugated electrolyte membrane was developed and tested. To increase the electrochemically active surface area, yttria-stabilized zirconia membranes with thickness of 70 nm were deposited onto prepatterned silicon substrates. Fuel cell performance of the corrugated e…
Chalcogenide glasses are widely used in phase-change nonvolatile memories and in optical recording media for their ability to rapidly change their structure to crystalline, thus obtaining different electrical resistance and optical reflectivity. Chalcogenide glasses universally display threshold switching, that is a s…
Control of function through the primary structure of a molecule presents a significant challenge with valuable rewards for nanoscience. Dendritic building blocks encoded with information that defines their three-dimensional shape (e.g., flat-tapered or conical) and how they associate with each other are referred to as…
[Reaction: see text]. Plasmonic-based chemical sensing technologies play a key role in chemical, biochemical, and biomedical research, but basic research in this area is still attracting interest. Researchers would like to develop new types of plasmonic nanostructures that can improve the analytical figures of merit,…
In this Letter, we calculate the electron-phonon coupling of the newly discovered superconductor LaFeAsO1-xFx using linear response. For pure LaFeAsO, the calculated electron-phonon coupling constant lambda=0.21 and logarithmic-averaged frequency omegaln=206 K give a maximum Tc of 0.8 K, using the standard Migdal-Elia…
The ternary iron arsenide ${\text{BaFe}}_{2}{\text{As}}_{2}$, with the tetragonal ${\text{ThCr}}_{2}{\text{Si}}_{2}$-type structure, exhibits a spin-density-wave (SDW) anomaly at 140 K, very similar to LaFeAsO, which is the parent compound of the iron arsenide superconductors. ${\text{BaFe}}_{2}{\text{As}}_{2}$ is a p…