Materials Literature
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We develop a continuum description of partially fluidized granular flows. Our theory is based on the hydrodynamic equation for the flow coupled with the order parameter equation which describes the transition between flowing and static components of the granular system. This theory captures important phenomenology rec…
We describe a new technique to determine the homogeneous linewidths of surface plasmon resonances of metal nanoparticles and thus measure the decay time of this collective electron excitation. The method is based on spectral hole burning and has been applied to supported oblate Ag particles with radii of 7.5 nm. From…
Cubic perovskite compounds of the form (A(1/3)A(')(1/3)A(")(1/3))BO3 and A(B(1/3)B(')(1/3)B(")(1/3))O3, in which the differentiated cations form an alternating series of monolayers, are studied using first-principles methods. Such compounds are representative of a possible new class of materials in which ferroelectric…
The relaxation process of one dimensional surface modulations is re-examined. Surface evolution is described in terms of a standard step flow model. Numerical evidence that the surface slope, D(x,t), obeys the scaling ansatz D(x,t)=alpha(t)F(x) is provided. We use the scaling ansatz to transform the discrete step mode…
Individual single-walled carbon nanotubes (SWNT) exhibiting small band gaps on the order of 10 meV are observed for the first time in electron transport measurements. Transport through the valence or conduction band of a small-gap semiconducting SWNT (SGS-SWNT) can be tuned by a nearby gate voltage. Intrinsic electric…
Optical second harmonic spectroscopy is introduced as a powerful supplement for the determination of complex magnetic structures. Experimental efforts are simplified and new degrees of freedom are opened. Thereby, some principal or technical restrictions of neutron or magnetic x-ray diffraction experiments are overcom…
Dielectric loss spectra of glass-forming propylene carbonate and glycerol at temperatures above and below T(g) are presented. By performing aging experiments lasting up to five weeks, equilibrium spectra below T(g) have been obtained. During aging, the excess wing, showing up as a second power law at high frequencies,…
The results of studies of patterned growth of vertically aligned carbon nanofibers (VACNFs) prepared by plasma-enhanced chemical vapor deposition are reported. Nickel (Ni) dots of various diameters and Ni lines with variable widths and shapes were fabricated using electron beam lithography and evaporation, and served…
The mechanical response of 15 single wall carbon nanotube (SWCNT) ropes under tensile load was measured. For 8 of these ropes strain data were obtained and they broke at strain values of 5.3% or lower. The force-strain data are well fit by a model that assumes the load is carried by the SWCNTs on the perimeter of each…
In an experiment on binary alloys directionally solidifying from below, Sample & Hellawell (1984) showed that the plume convection can be successfully prohibited by rotating the cooling tank around an inclined axis. In the present paper we interpret their experimental observation by an analytical approach. Results…
Multi-material Eulerian methods were originally developed to solve problems in hypervelocity impact. They have proven to be useful for many other problems involving high-strain rates such as the dynamic compaction of a powder and high-speed machining. An implicit formulation has been developed to extend the range of a…
The structures and UV absorption spectra of (AgBr) n clusters ( n = 1−9) are investigated in both the gas phase and in a dielectric medium. The structures of clusters were determined at the B3P86 level using a moderate size basis set with full geometry optimization. For clusters with n = 1−6, extensive searches of the…
The modification of layered transition metal dichalcogenides through intercalation is reviewed, with special emphasis on in situ intercalation with alkali metals. Experimental results obtained using photoelectron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy and transmission electron mic…
We present the first ab initio density functional theory study of the oxygen-terminated Cr 2 O 3 (0001) surface within the local spin-density approximation (LSDA). We find that spin plays a critical role for even the most basic properties of Cr 2 O 3, such as the structure and mechanical response of the bulk material.…
We present a three-dimensional (3D) analysis of subwavelength diffractive optical elements (DOE's), using the finite-difference time-domain (FDTD) method. To this end we develop and apply efficient 3D FDTD methods that exploit DOE properties, such as symmetry. An axisymmetric method is validated experimentally and is…
The reversible partitioning of molecules between immiscible phases, such as in solvent extraction, is usually controlled by chemical composition of one or both phases, temperature, or pH. An additional means for controlling the equilibrium distribution of a solute between phases, the use of light and suitable photochr…
Single crystals of [Ag(CN) 2 - ]/NaCl and [Ag(CN) 2 - ]/KCl show luminescence spectra that change drastically with temperature. The major luminescence band at 12 K is a UV emission at about 315 nm. Blue-green emissions in the 400−520 nm region appear upon an increase in temperature to 80 K. A further increase in tempe…
Magnetic coupling constants J for the complete structures of heterobinuclear compounds GdCu(OTf) 3 (bdmap) 2 (H 2 O)·THF ( 1, Gd III Cu II ), [Gd(C 4 H 7 ON) 4 (H 2 O) 3 ][Fe(CN) 6 ]·2H 2 O ( 2, Gd III Fe III ), and [Gd(C 4 H 7 ON) 4 (H 2 O) 3 ][Cr(CN) 6 ]·2H 2 O ( 3, Gd III Cr III ) have been calculated by the combin…
The adsorption behavior of 1,3-propanedithiol (1,3-PDT) on a colloidal gold surface has been investigated by means of surface-enhanced Raman scattering (SERS). 1,3-PDT chemisorbed dissociatively on gold as a monothiolate. Moreover, we could clearly identify the S−S stretching band that reveals the formation of multila…
We report the normal stresses in a non-Brownian suspension in plane Couette flow determined from Stokesian Dynamics simulations. The presence of normal stresses that are linear in the shear rate in a viscometric flow indicates a non-Newtonian character of the suspension, which is otherwise Newtonian. While in itself o…