Materials Literature
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Iron-rich intermetallic compounds Sm2Fe17−xSix and Sm2Fe17−xSixC (x=0, 1, 2, and 3) were studied. The as-prepared compounds are single phase with the rhombohedral Th2Zn17-type structure except for Sm2Fe17C and Sm2Fe16SiC which contain some amounts of α-Fe. The unit cell volumes and saturation magnetization at room tem…
As a result of the interaction between the spin and the magnetic field (B), special step structures are predicted to exist in the ballistic magnetoconductance of carbon nanotubes. The electronic structure of a carbon nanotube drastically changes from a metal (semiconductor) to a semiconductor (metal) during the variat…
The thermo-emf in bipolar semiconductors is calculated. It is shown that it is necessary to take into account the nonequilibrium distribution of electron and hole concentrations (Fermi quasilevels of the electrons and holes). We find that electron and hole electric conductivities of contacts of semiconductor samples w…
The influence of Sb, As, Ga, and In as surfactants on the Si/Si(111) homoepitaxy is studied using scanning tunneling microscopy. The nucleation of two-dimensional (2D) Si islands on the surfactant-terminated surface was studied as a function of temperature. The island densities and depleted zones show Arrhenius behavi…
The hydrodynamic model for the degenerate free-electron gas has been generalized for arbitrary frequencies. The result for the longitudinal dielectric function is \ensuremath{\epsilon}(\ensuremath{\omega},q)=1-${\mathrm{\ensuremath{\omega}}}_{\mathit{P}}^{2}$[\ensuremath{\omega}(\ensuremath{\omega}+i\ensuremath{\nu})-…
Using chemical-vapor deposition nanodispersed silicon has been prepared in carbon at temperatures between 850 and 1050 °C. Samples with up to 11% atomic silicon in carbon show the same pregraphitic x-ray-diffraction pattern as those without silicon. X-ray-absorption spectroscopy shows that the silicon is bonded mostly…
The stability of interfaces and the mechanisms of thin film growth on semiconductors are issues of central importance in electronic devices. These issues can only be understood through detailed study of the relevant microscopic processes. Experimental studies are able to provide detailed, atomic scale information for…
Ab initio molecular dynamics is used to study deformations of sodium clusters at temperatures $500\cdots 1100$ K. Open-shell Na$_{14}$ cluster has two shape isomers, prolate and oblate, in the liquid state. The deformation is stabilized by opening a gap at the Fermi level. The closed-shell Na$_8$ remains magic also at…
Using the non-empirical Variational Induced Breathing (VIB) model, the thermal properties of periclase (MgO) under high pressures and temperatures are investigated using molecular dynamics, which includes all anharmonic effects. Equations of state for temperatures up to 3000K and pressures up to 310 GPa were calculate…
Adaptive coordinates are shown to be effective in allowing the accurate calculation of structures and interatomic forces for solids containing first-row atoms using relatively small orthonormal sets of basis functions. Several polymorphs of ${\mathrm{SiO}}_{2}$ are studied as illustrative test cases.
Local-density-functional pseudopotential theory is used to investigate native defects in diamond, their structure, electronic, vibrational, and diffusive properties. We find the only truly stable structure for an interstitial atom to be the 〈100〉 split interstitial defect. This conclusion holds in the neutral, -1, +1,…
We have investigated the adsorption and thermal conversion of molecular oxygen (O2) states on the TiO2(110) surface by making use of the distinct photodesorption behavior of each adsorption state. Oxygen chemisorbs at the oxygen vacancy defect sites on the annealed TiO2(110) surface at 105 K to a saturation coverage o…
High-quality, size-selected, nano-size (2--15 nm\ifmmode\pm\else\textpm\fi{}10%) clusters of ${\mathrm{MoS}}_{2}$ have been successfully grown inside inverse micellar cages and their optical properties have been studied. These clusters exhibit (1) large blueshifts in the optical-absorption features with decreasing clu…
Potassium fluoroboratoberyllate KBe2BO3F2 (KBBF) has been revealed theoretically and experimentally as a novel ultraviolet nonlinear optical crystal, but it is found to be very difficult to grow in a large size, because of the weak binding interaction between the (Be2BO3)∞ units, which leads to an apparent layer habit…
We report low-temperature absorption, time-integrated photoluminescence, and resonant-Raman-scattering spectra near the fundamental band gap of ${\mathrm{TiO}}_{2}$ single crystals. The photoluminescence spectrum comprises a first peak at \ensuremath{\Elzxh}\ensuremath{\omega}=3.031 eV, followed by several peaks at lo…
Structural transformations in CdSe nanocrystals are studied using high pressure x-ray diffraction and high pressure optical absorption at room temperature. The nanocrystals undergo a wurtzite to rock salt transition analogous to that observed in bulk CdSe. Both the thermodynamics and the kinetics of the transformation…
The quasiparticle band structure of bulk hexagonal boron nitride is studied within the GW approximation for the self-energy operator. The influence of the interlayer distance on the band structure is investigated both within the local density approximation and the quasiparticle approach, and the importance of an inter…
Abstract The liquefied wood resins obtained by liquefying wood in the presence of phenol using phosphoric acid as a catalyst were applied to prepare the moldings by using hexamine as a hardener. The effects of the molding conditions and the moldings' compositions on flexural properties and water‐sorption kinetics of t…
We propose two different macroscopic dynamics to describe the decay of metastable phases in many-particle systems with local interactions. These dynamics depend on the macroscopic order parameter $m$ through the restricted free energy $F(m)$ and are designed to give the correct equilibrium distribution for $m$. The co…
Erbium surface segregation is observed during growth of Er-doped Si by molecular beam epitaxy on Si(100) at 600 °C. Once a critical Er surface areal density of 2×1014 Er/cm2 is reached, enhanced Er trapping is observed, possibly due to the formation of silicide precipitates. Er segregation on Si(100) is fully avoided…