Materials Literature
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The compound LiAl_yTi_(2-y)O_4 undergoes a metal-to-insulator transition for y_c ~0 .33. This system, in the absence of strong electronic correlations, is a prototypical example of quantum site percolation. However, it is known that the effects of disorder produced by such a percolating lattice are insufficient to exp…
Quasiclassical boundary conditions for electrochemical potentials at the interface between diffusive ferromagnetic and non-magnetic metals are derived for the first time. An expression for the boundary resistance accurately accounts for the momentum conservation law as well as essential gradients of the chemical poten…
Based on the work of Gorling and that of Levy and Nagy, density-functional formalism for many Fermionic excited-states is explored through a careful and rigorous analysis of the excited-state density to external potential mapping. It is shown that the knowledge of the ground-state density is a must to fix the mapping…
We performed first principles density functional calculations and simulations of magic-size neutral NaCl nanocubes, and computed the the extraction of a Na neutral corner atom after donating an electron. The atomic structure of the resulting Na corner vacancy is presented.
We report on the growth of epitaxial bilayers of the La2∕3Sr1∕3MnO3 (LSMO) half-metallic ferromagnet and the BiFeO3 (BFO) multiferroic, on SrTiO3(001) by pulsed laser deposition. The growth mode of both layers is two dimensional, which results in unit-cell smooth surfaces. We show that both materials keep their proper…
Here we make use of the Hellmann-Feynman theorem, with the aim to calculate macroscopic quantum velocities instead of forces, and we show how it is possible to derive the expression of the work per unit time, per unit volume (power density) done by a static external uniform electromagnetic field interacting with a qua…
In light of the recent work by Sahni et al., Harbola, and Gaudoin and Burke, the question of mapping from an excited-state density of a many-electron interacting system to the potential of the related non-interacting system is analyzed. To do so, we investigate the Levy-Nagy criterion quantitatively for several excite…
In this paper we make use of the concept of conserved geometric phase and of group velocity,in conjunction with the representation theory\cite{Dirac,Dirac-letture}, in order to derive some relevant physical quantities for the description of the dielectric and magnetic response of crystalline materials. As an applicati…
We report spectral features of far infrared electromagnetic radiation absorption in anatase TiO2 nanopowders which we attribute to absorption by acoustic phonon modes of nanoparticles. The frequency of peak excess absorption above the background level corresponds to the predicted frequency of the dipolar acoustic phon…
We show that sputtered, pure epitaxial iron films can have high-frequency loss as low as, or lower than, any known metallic ferromagnetic heterostructure. Minimum 34 Ghz ferromagnetic resonance (FMR) linewidths of 41 Oe are demonstrated, some ~ 5-10 % lower than the previous minimum reported for molecular beam epitaxi…
An exchange energy functional is proposed and tested for obtaining a class of excited-state energies using density functional formalism. The functional is the excited-state counterpart of the local-density approximation functional for the ground state. It takes care of the state dependence of the energy functional and…
This paper deals with Hamiltonians of the form $H=-{\bf \nabla}^2+v(\rr)$, with $v(\rr)$ periodic along the $z$ direction, $v(x,y,z+b)=v(x,y,z)$. The wavefunctions of $H$ are the well known Bloch functions $ψ_{n,λ}(\rr)$, with the fundamental property $ψ_{n,λ}(x,y,z+b)=λψ_{n,λ}(x,y,z)$ and $\partial_zψ_{n,λ}(x,y,z+b)=…
The piezoelectric and ferroelectric properties of [Bi0.5(Na1−x−yKxLiy)0.5]TiO3 (BNKLT-x∕y) lead-free piezoelectric ceramics were studied. The ceramics show excellent piezoelectric and ferroelectric properties, and the optimum properties measured are as follows: piezoelectric constant d33=231pC∕N, planar and thickness…
Nanoporous carbon (NPC) exhibits unexplained chemical properties, making it distinct from other graphenelike materials, such as graphite, fullerenes, or nanotubes. In this Letter, we analyze the properties of NPC in terms of its structural motifs, which are derived from defects in distorted graphene sheets. Our densit…
The performance of photovoltaic and photochemical devices is directly linked to the efficiency with which absorbed photons are converted into electron-hole pairs (excitons). A usual assumption is that one photon produces a single exciton, while the photon energy in the excess of the material's energy gap (the gap that…
The seed-mediated approach to making gold nanorods in aqueous surfactant solutions has become tremendously popular in recent years. Unlike the use of strong chemical reductants to make spherical gold nanoparticles, the growth of gold nanorods requires weak reducing conditions, leading to an unknown degree of gold redu…
Abrasion is responsible for many surface changes that occur on garments. For this reason, the evaluation of its effects becomes very important for the textile industry. In particular, pilling formation is a phenomenon that results of the abrasion process and affects fabrics more significantly altering their surface se…
Abstract Lateral control of template synthesis in nanoporous alumina membranes (NAMs) was previously shown by us to enable preparation of graded composite materials. Formation of thickness gradients of Cu was demonstrated using electrodeposition (or electrodissolution) of Cu in the NAM template under a lateral voltage…
The development of a high-yield and low environmental impact synthesis able to deliver highly pure pergolide mesylate 1 is described. The process [seven chemical steps (four telescoped), three steps of isolation of intermediate, and only one drying] affords pergolide mesylate 1 in 75−81% overall yield from dihydrolyse…
We have studied the electronic structure of the oxygen-deficient type perovskite ${\mathrm{TbBaCo}}_{2}{\mathrm{O}}_{5.5}$, ${\mathrm{NdBaCo}}_{2}{\mathrm{O}}_{5.5}$, and ${\mathrm{NdBaCo}}_{2}{\mathrm{O}}_{5}$ using x-ray photoemission spectroscopy. The valence-band photoemission spectrum of ${\mathrm{TbBaCo}}_{2}{\m…