Summary Specific heat data and their relation to the form of the energy gap are reviewed for Al, HfV2, and two recently discovered superconductors, MgB2 and Na0.3CoO2·1.3H2O. The data for Al and HfV2 exemplify the specific heat of, respectively, weak- and strong-coupled BCS superconductors with isotropic energy gaps. MgB2 is also known to be a BCS superconductor, but the specific heat deviates from BCS behavior in a way that shows the presence of two distinctly different energy gaps and characteristics of both weak and strong coupling. The heat capacity of Na0.3CoO2·1.3H2O is strongly sample dependent, but suggests that it is another two-gap, possibly ‘unconventional’ superconductor.
A numerical study of the thermodynamic properties of a superconducting quantum cylinder in a longitudinal magnetic field is carried out. Closed-form expressions for the critical temperature, the free energy, the heat capacity jump, and the magnetization difference between the superconducting and normal phases as functions of the nanotube parameters are obtained in limit cases.
Authors:Abolfazl Shiroudi, Ehsan Zahedi, and Reza Zabihi
occupancies of LP(e) x1 nonbonding orbitals in the rings of compounds 1 – 3 (1 < 3 < 2). The results revealed that by the increase of electronegativity of atom X (O, S, N), resonance energies increase and the HOMO-LUMO energy-gaps in the ground state
Authors:A. A. Abd El-Rahman, K. K. Tahoon, Abd El-Salam, M. Abousehly, Abd Elwahab, and A. El-Sharkawy
The specific heat (Cp), thermal conductivity (λ), thermal diffusivity (a), and electrical conductivity (σ) were measured for polycrystalline HgS and Sb2S3 in the temperature range 300–600 K. The measurements were performed with an experimental apparatus based on a socalled flash method. The results showed that the mechanism of heat transfer is mainly due to phonons, whereas the contribution of electrons and bipolars is very small indeed. The energy gap of the samples was also calculated.
Thick targets (mica) and thin hydrogen layers obtained by ionic implantation of protons in silica are used to establish the
excitation function of the nuclear resonant reaction1H (15N, α γ)12C. Two main resonances in the energy gap explored were observed. Their FWHM and the cross section at ER are specified. The experimental conditions required and the performances allowed, using this reaction to determine hydrogen
depth profiles in the near surface region of solids, are presented. Examples concerning borosilicates, leached in aqueous
medium, are given.
Authors:Kwang-Pill Lee, Keung-Shik Park, Duck-Won Kang, Yasuhiro Yamada, and Shin-ichi Ohno
The mechanism of the reduction reaction of lanthanide(III) ions by hydrated electrons in polar solvents has been investigated.
The theoretical rate constants for the reaction of hydrated electrons with a number of lanthanide ions have been calculated
using the energy gap laws of the charge shift reaction(D+−A→D−A+) and compared with experimental values. With these results, we have explained the large difference of the reaction rates
of lanthanide ions with hydrated electrons, which depend upon the kind of lanthanide ion. The calculated results agree almost
quantitatively with the experimental values.
Authors:M. S. Masoud, S. A. El-Enein, and E. El-Shereafy
Electrical conductivity properties of someo-substituted arylazo-barbiturate complexes at different temperatures are studied. The σo, ΔE andEg values are determined. The copper complexes derived from −H, −CH3 and −OCH3 substituted organic compounds are with semiconducting properties at low temperatures and insulator at high temperatures. All the carboxy and the cobalt and the the nitro complexes, and nickel-methyl complexes are of semiconducting behaviour. The data are explained in the light of extrensic and lattice vibrations and the width of the forbidden energy gap properties.
The atomic superposition and electron delocalization molecular orbital (ASED-MO) theory was used to calculate structures and
relative stabilities of metformin-metal complexes. The relative stabilities and decomposition pathways were discussed in terms
of bond order, binding energy and the nature of charge on the central metal atom. The electronic transitions and their energy
gaps were also studied. The optimization of the structures shows that the most stable state is distorted from planarity for
CoII and NiII complexes.
Different samples of Sr-ferrites have been synthesized by the usual ceramic and high temperature sintering technique. On these samples, several measurements have been undertaken namely, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), the temperature dependence of DC electric conductivity before and after -absorbed dose, and the temperature dependence of dielectric constant. Results obtained were explained, correlated, interpreted and discussed in detail on the basis of the interaction of temperature, dopant cations and -radiation with the Sr-ferrite lattice. The activation energy (E), energy gap for semiconduction and activation energy for -radiation-induced carrier liberation () were evaluated for the first time. Finally, a mechanism for semi-conductivity in terms of energy band picture in intrinsic ferrite semiconductors is suggested and discussed.
Various samples of different substituted Laferrites La1–xSmx1 (Fe1–x2Bx2)O3 have been prepared by the usual ceramic procedure and firing technique. On these samples, numerous measurements have been performed, namely, thermogravimetric analysis (TGA), differential scanning calorimetry, the temperature dependence of electrical conductivity before and after -absorbed dose (4.5×107 rad) and the temperature dependence of dielectric constant. Results obtained were explained, interpreted and discussed in detail on the basis of interaction of the dopant cations and ionizing radiation with La-ferrite lattice. Furthermore, the thermal stability, activation energy and energy gap for semiconduction of the investigated ferrites were evaluated before and after -absorbed dose (4.5×107 rad). Finally, the activation energy for -radiation induced carrier liberation in La-ferrites was evaluated for the first time.