Materials Literature
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We present ab initio local-density-functional calculations of the electronic structure of clean and hydrogenated diamond (110) surfaces. The clean surface relaxes to a structure where the chains in the first two planes are straightened so that the interatomic distances are shortened and the bond angles are increased.…
The electrical and electroluminescence characteristics of heterostructure systems containing thin films of visibly emitting silicon nanoparticles are shown to be controlled by carrier transport through the nanoparticulate films. A conduction mechanism encompassing both geometric and electronic effects most effectively…
The behavior of simple fluids under shear is investigated using molecular dynamics simulations. The simulated system consists of a fluid confined between two atomistic walls which are moved in opposite directions. Two approaches for shear flow simulations are compared: in one case, the sheared fluid is not thermostatt…
Detailed molecular mechanism of polymer crystallization into the chain folded lamella is investigated by molecular dynamics simulation. Though the crystallization of polymer is generally a very slow process that seems to defy every computational approach, simplifications of the computational model are found to improve…
Diamond exhibits very high, but widely varying, secondary-electron yields. In this study, we identified some of the factors that govern the secondary-electron yield from diamond by performing comparative studies on polycrystalline films with different dopants (boron or nitrogen), doping concentrations, and surface ter…
The delafossite-type ${\mathrm{CuFeO}}_{2}$ single crystal was studied by means of x-ray emission and x-ray photoelectron spectroscopy. The valence state of Cu ions was found to be $1+,$ whereas Fe ions were found to be trivalent in the high-spin $S=5/2$ state. The x-ray emission (Cu ${L}_{\ensuremath{\alpha}},$ Fe ${…
The local spin-density approximation+$U$ method has been applied to identify the origin of surface electronic states on the (100) surface of nickel monoxide. The results of ab initio calculations show a substantial reduction of the forbidden gap at the surface and point to the presence of two types of electronic state…
Argon gas was trapped at high pressure within hollow carbon tubes grown in vapor that have an outer diameter of between 20 and 150 nanometers. The gas was forced into the tubes by hot isostatically pressing (HIPing) the carbon material for 48 hours at 650°C under an argon pressure of 170 megapascals. Energy dispersive…
The electric field induced phase transition behavior of lead lanthanum zirconate titanate stannate (PLZTS) ceramics was investigated. PLZTS undergoes a tetragonal antiferroelectric (AFETet) to rhombohedral ferroelectric (FERh) phase transition with the application of an electric field. The volume increase associated w…
Through the use of relations analogous to that of the Rayleigh law, it is demonstrated that the ac electric field dependence of the permittivity of ferroelectric thin films can be described. It is further shown that both reversible and irreversible components of the permittivity decrease linearly with the logarithm of…
Macrostrain variations in engineering components are frequently examined using neutron diffraction, at both reactors and pulsed sources. It is desirable to minimize the sampling volume in order to maximize the spatial resolution, although this increases the required measurement time. At reactors, macrostrain behavior…
It is shown that at weak alternating stress the relationship between the piezoelectrically induced charge and applied stress in ferroelectric ceramics has the same form as the Rayleigh law for magnetization versus magnetic field in ferromagnetic materials. Applicability of the Rayleigh law to the piezoelectric effect…
The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn1/3Nb2/3)O3–PbTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O3, morphotropic phase boundary compositions were not essential for high…
Both off-Bragg and Bragg blazing phenomena, observed in a periodic strip grating over a grounded dielectric, are described, along with some discussion of the differences of the blazing phenomena in this geometry in comparison with those of the previous rectangular groove geometry.
Quantum well infrared photodetectors do not respond to normal incident light due to the quantum mechanical selection rules associated with intersubband transitions. Thus alternate light coupling systems, such as gratings are required in order to deflect the incoming light away from the normal. The resolution of the ph…
The one-step model of valence-band photoemission and inverse photoemission from single-crystal surfaces is reformulated for generalized (non-local, complex and energy-dependent) potentials. Thereby, it becomes possible to account for self-energy corrections taken from many-body electronic-structure calculations. The o…
We present a novel method for the calculation of the static and electronic dielectric tensor of polar insulating crystals based on concepts from the modern theory of dielectric polarization. As an application, we present the first ab initio calculation of the dielectric constants in the wurtzite III-V nitrides AlN, Ga…
The ${}^{27}$Al and ${}^{63}$Cu spin-lattice relaxation rates were found to contain a large ${T}^{2}$ term over a wide temperature range below 400 K in several thermodynamically stable quasicrystalline alloys, including $i$-AlCuRu, $i$-AlPdRe, $i$-AlCuFe, and the crystalline approximant phase \ensuremath{\alpha}-AlMnS…
Numerically minimizing a continuous free-energy functional which yields several modulated phases, we obtain the order-parameter profiles and interfacial free energies of symmetric and nonsymmetric tilt boundaries within the lamellar phase, and of interfaces between coexisting lamellar, hexagonal, and disordered phases…
Entropically stabilized quasicrystals are usually modeled as equilibrium ensembles of random tilings. In several models, such as the two-dimensional square-triangle tiling studied here, the corresponding kinetics may be very slow because a large number of tiles must be rearranged at each step through the ensemble. Her…