Spectral shift function for a discretized continuum

A spectral shift function (SSF) is an important object in the scattering theory which is related both to the spectral density and to the scattering matrix. In the paper, it is shown how to employ the SSF formalism to solve scattering problems when the continuum is discretized, e.g. when solving a scattering problem in a finite volume or in the representation of some finite square-integrable basis. A new algorithm is proposed for reconstructing integrated densities of states and the SSF using a union of discretized spectra corresponding to a set of Gaussian bases with the shifted scale parameters. The examples given show that knowledge of the discretized spectra of the total and asymptotic Hamiltonians is sufficient to find the scattering partial phase shifts at any required energy, as well as the resonances parameters.

Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir

Ti3Sb and Ti3Ir adopt the A15 (Cr3Si type) structure and are reported to incorporate hydrogen atoms to an extent, respectively, of Ti3SbH∼3 and Ti3IrH3.8. First-principles electronic structure calculations were performed to identify factors contributing to the difference in maximum hydrogen composition for these two intermetallic compounds. Relative energies and changes in energy densities of states and crystal orbital Hamilton populations upon H insertion in the intermetallic compounds were examined. In both compounds, hydrogen atoms are attracted to [Ti4] tetrahedral interstitial sites over any others. The natures of metal-hydrogen and metalloid-hydrogen bonding and the effects of hydrogen insertion on metal-metal and metal-metalloid bonding have an influence on the maximum hydrogen contents for Ti3Sb and Ti3Ir.

Carbazochrome Carbon Nanotube as Drug Delivery Nanocarrier for Anti-bleeding Drug: Quantum Chemical Study

The interaction between drugs and single-walled carbon nanotubes is proving to be of fundamental interest for drug system of delivery and nano-bio-sensing. In this study, the interaction of pristine CNT with carbazochrome, an anti-hemorrhagic or hemostatic agent was investigated with M06-2X functional and 6-31G* and 6-31G** basis sets. All probable positions of related adsorption for these kind drugs were thought-out to find out which one is energetically suitable. Based on the achieved data, the stronger interactions appeared the oxygen atom of C=O group and nitrogen atom of imine groups. The topology analysis of QTAIM (quantum theory of atoms in a molecule) method was accomplished to understand the properties of interactions between the CNT and Carbazochrome. Frontier molecular orbital energies of all systems, global index including stiffness, softness, chemical Gibbs energies and electrophilicity parameters, as well as some other important physical data such as dipole moment, polarizability, anisotropy polarisibility and hyperpolaribility were calculated, evaluated and then compared together. The essence of the formed bonding model progress along the reaction roots were further validated using electron localization function (ELF) calculations. In addition the total, partial, and overlapping population densities of states were calculated for any further discussion. The highest values of adsorption energies were determined in the range of 18.24) up to (22.12) kcal mol-1 for these kind systems. The acceptable recovery time of 849 s was obtained for the desorption of carbazochrome from the CNT surface under UV-Light. The final results exhibit that carbazochrome can serve as a promising carrier and also as sensitive sensors in any kind of practical application.

Green Afterglow of Undoped SrAl2O4

Undoped SrAl2O4 nanocrystals were obtained via solution combustion using urea as fuel. The afterglow properties of undoped SrAl2O4 were investigated. Green afterglow from undoped SrAl2O4 is visible to the human eye when the 325 nm irradiation of a helium–cadmium laser (13 mW) is ceased. The afterglow spectrum of undoped SrAl2O4 is peaked at about 520 nm. From the peak temperature (321 K) of the broad thermoluminescence glow curve, the trap depth of trap levels in undoped SrAl2O4 is estimated to be 0.642 eV using Urbach’s formula. Based on first-principles density functional calculations, the bandstructures and densities of states are derived for oxygen-deficient SrAl2O4 and strontium-deficient SrAl2O4, respectively. Our results demonstrate that the green afterglow of undoped SrAl2O4 originates from the midgap states introduced by oxygen and strontium vacancies. The observation of green afterglow from undoped SrAl2O4 helps in gaining new insight in exploring the afterglow mechanisms of SrAl2O4-based afterglow materials.

The chemical potential for a semiconductor

“The chemical potential for a semiconductor” deals with the way in which the chemical potential (Fermi level) of a semiconductor is affected: by the densities of states in the bands; by temperature; and by doping. The electron–hole product is usually independent of doping but sensitive to temperature. The chemical potential is worked out numerically for an example case, and is shown to be most sensitive to doping.