Narrow Results

Based on the consideration on size-dependent temperature T_m(D) where D denotes the diameter of nanoparticles and nanowires or the thickness of thin films, the size-dependent band-gap ΔE_g(D) and dielectric constant ε(D) of low dimensional materials are modeled without any adjustable parameter. The model predicts an increase of the band-gap and a decrease of dielectric constant with drop of Si nanocrystals' size. The predicted results correspond to experimental and computer simulation results of Si nanocrystals.

Structural and electronic properties of perovskite KCaX₃ (X = F and Cl) compounds are investigated using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k code. The exchange-correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Based on these calculations, it has been concluded that KCaX₃ compounds have indirect energy band-gap (Γ-R). Moreover, the theoretical investigation which has been carried out on the highly hydrostatic pressure dependence of the KCaX₃ electronic properties revealed a linear relationship between both the hydrostatic pressure and the energy band-gap. In addition, the electronic and bonding properties of the band structure, density of states (DOS) and electron charge density have been calculated and presented. Besides that, the dielectric function, refractive index and extinction coefficient are calculated. The origin of some of the peaks in the optical spectra is discussed in terms of the calculated electronic structure. Finally, the calculated structural properties are found to agree well with the available experimental and theoretical data.

Different ways to chaos show different features. The study of Sudden Occurrence of Chaos has generated much interest in exploring new ways to chaos. In this novel way, the Sudden Occurrence of Chaos-II indicates more comprehensive dynamical behaviors than Sudden Occurrence of Chaos. The Sudden Occurrence of Chaos-II not only belongs to the previous category of Sudden Occurrence of Chaos, but also includes inverse period-doubling band splitting, and a series of "band-gaps" by successive splitting of bands, which do not appear in the previous case. The constant of inverse period-doubling splitting band is first calculated, which is completely different from the first Feigenbaum constant. Furthermore, we give some examples of m-period Sudden Occurrence of Chaos-II by regulating periodic parameter m.

We report here the weak quantum confinement effect in zinc oxide nanorods fabricated by a simple wet chemical method at room temperature. The formation of nanorods was confirmed through X-ray diffraction measurements. The particle size was also determined from the X-ray diffraction pattern and was found to be 20 nm. The band gap was calculated from the UV-Visible spectrum and found to be 3.72 eV, which is higher as compared to the bulk ZnO. It owes its value to the quantum confinement effect. However, the large particle size indicates that the confinement is weak in nature. The photoluminescence spectrum shows a strong emission peak at 421 nm accompanied by several much weaker defect related emissions in the visible region. Using the weak confinement model, we identified the transition levels for those emissions.