Materials Literature
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The full-potential augmented plane wave plus local orbital method within density-functional theory is used to predict that MnBi in the zinc-blende structure is a true half-metallic ferromagnet with a magnetic moment of $4.000{\ensuremath{\mu}}_{B}$ per formula unit. This contrasts with the zinc-blende phase of MnAs, w…
In recent years, the Preisach hysteresis model (1935) has emerged as the model of choice for the behaviour of many smart materials, such as shape memory alloys (SMA). This research treats the identification of Preisach models for a differential SMA actuator. The traditional identification technique is applied, and sev…
The symmetry breaking effects for quantum tunneling of the magnetization in Mn12-acetate, a molecular nanomagnet, represent an open problem. We present structural evidence that the disorder of the acetic acid of crystallization induces sizable distortion of the Mn(III) sites, giving rise to six different isomers. Four…
Control of particle-particle spacing is a key determinant of optical, electronic, and magnetic properties of nanocomposite materials. We have used poly(amidoamine) (PAMAM) dendrimers to assemble carboxylic acid-functionalized mixed monolayer protected clusters (MMPCs) through acid/base chemistry between the particle a…
Large scale molecular dynamics (MD) simulations are used to simulate the plastic deformation of a nanocrystalline model Ni sample with an average grain size of 5 nm containing 125 grains at 800 K up to 4.0% plastic strain. For the first time in MD simulation, emerging shear planes involving several grain boundaries ha…
Single-walled carbon nanotubes (SWNTs) can react with potassium hydroxide through a simple solid-phase mechanochemical reaction at room temperature to produce single-walled carbon nanotubols (SWNTols) − multiple hydroxyl groups direct-modified SWNTs. The SWNTols are highly soluble in water and can be readily self-asse…
The literature proposes some thermal models needed for the electrothermal simulation of power electronic systems. This paper gives a useful analysis about the choice of the thermal model circuit networks, equivalent to a discretisation of the heat equation by the finite difference method and the finite element method…
HT-poly(3-hexylthiophenes) (HT-PHT) with H/Br end group composition were prepared via a modified McCullough method using anhydrous ZnCl 2 for the transmetalation step. These bromine-terminated HT-PHT can be end group modified at the ω end through a cross-coupling reaction with thienylzinc compounds bearing a THP-prote…
An advanced type thermoelectric module based on SiGe has been developed to apply it to gasoline engine vehicles. The size of the module is 20 mm square and 9.2 mm in height. The module consists of 8 couples of p- and n-type Si-Ge elements. The elements are electrically connected in series using Mo electrodes by brazin…
Being motivated by recent experimental studies, we investigate magnetic structures of the Mo pyrochlores $A_2$Mo$_2$O$_7$ ($A$= Y, Nd, and Gd) and their impact on the electronic properties. The latter are closely related with the behavior of twelve Mo($t_{2g}$) bands, located near the Fermi level and well separated fr…
We report on experiments in which a spin-polarized current is injected from a $GaMnAs$ ferromagnetic electrode into a $GaAs$ quantum well through an AlAs barrier. The resulting spin polarization in the GaAs well is detected by measuring how the current, tunneling to a second $GaMnAs$ ferromagnetic electrode, depends o…
We present the analytical study of stability loss and evolution of domain structure in inhomogeneous ferroelectric (ferroelastic) samples for exactly solvable models. The model assumes a short-circuited ferroelectric capacitor (free ferroelastic) with two regions with slightly different critical temperatures ${T}_{c1}…
We study the Landau-Zener-Stueckelberg (LZS) effect for a two-level system with a time-dependent nonlinear bias field (the sweep function) $W(t).$ Our main concern is to investigate the influence of the nonlinearity of $W(t)$ on the probability P to remain in the initial state. The dimensionless quantity $\ensuremath{…
We report on the characterization of torsional oscillators which use multiwalled carbon nanotubes as the spring elements. Through atomic-force-microscope force-distance measurements we are able to apply torsional strains to the nanotubes and measure their torsional spring constants, and estimate their effective shear…
Electronic structure calculations performed on very large supercells have shown that the local charge excesses in metallic alloys are related through simple linear relations to the local electrostatic field resulting from distribution of charges in the whole crystal. By including local external fields in the single si…
We solve a long-standing problem---determining structural information for disordered materials from their diffraction spectra---for the special case of planar disorder in close-packed structures (CPS's). Our solution offers the most complete possible statistical description of the disorder and, from it, we find the mi…
Recently Smit et al. [Nature 419, 906 (2002)] have reported that a single hydrogen molecule can form a bridge between Pt electrodes, which has a conductance close to one quantum unit, carried by a single channel. We present density functional calculations explaining these experimental findings. We show that the symmet…
We report resistivity measurements on epitaxial ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ films between 3 and 100 nm thickness grown on polished MgO substrates. The resistivity of the films is larger than the bulk resistivity, and is increasing with decreasing film thickness. This can be explained by the significant decreas…
The approach of the elastic continuum limit in small amorphous bodies formed by weakly polydisperse Lennard-Jones beads is investigated in a systematic finite-size study. We show that classical continuum elasticity breaks down when the wavelength of the solicitation is smaller than a characteristic length of approxima…
In this Account, we summarize some of our recent studies on the materials properties of the carbon nanotubes (CNTs). The focus is on single-wall carbon nanotubes (SWNTs). We describe experiments on synthesis of SWNTs with controlled molecular structures and assembly of functional macroscopic structures. In addition, w…