Direct evidence of Cd vacancies in CdSe nanoparticles: positron annihilation studies

Poly vinyl alcohol (PVA) capped CdSe nanoparticles having size in the range of 7–17 nm have been synthesized through chemical route and characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Positron coincidence Doppler broadening (CDB) measurements have been carried out in these nanoparticles. It is observed that the electron momentum distributions show a variation in the core electron momentum region with the particle size. In order to examine the influence of defects, first principle calculations of electron momentum distributions in bulk CdSe and in the presence of Cd as well as Se vacancy defects have been performed. Comparison of experimental data with the calculated momentum distribution reveals the presence of Cd vacancy defects, the concentration of which decreases with the increase in the particle size. The present study also indicates possible Se enrichment on the surface of the nanoparticles with the decrease in the particle size.     

The role of N dopant in inducing ferromagnetism in (ZnO)n clusters (n = 1-16)

The effect of nitrogen doping on the magnetic properties of (ZnO)(n) clusters (n = 1-16) has been investigated using spin polarized density functional theory. The total energy calculations suggest that N is more stable at the O site than at the Zn site in (ZnO)(n) clusters and induces a magnetic moment of 1 μ(B)/N atom. The N-Zn-N configuration is more stable than isolated N for 3D structures. The N dopants do not show any tendency for clustering. The binding energy is found to decrease with the increase in the number of N dopants. The magnetic moment increases gradually with the increase in the number of atoms with 1 μ(B)/N atom for n ≤ 4 and less than 1 μ(B)/N for n > 4. The local magnetic moment is mainly localized at the N site with a small magnetic moment induced at the O site. The presence of a Zn vacancy (V(Zn)) induced an additional magnetic moment of 2 μ(B) on the nearest O atoms. The N dopant prefers to form a N-V(Zn) pair. The combination of N and V(Zn) in 3D structures leads to a total magnetic moment of 3 μB. The Mulliken charge transfers from Zn to N and O in all N doped (ZnO)(n) clusters. The calculated results are consistent with existing experimental and theoretical results.     

In-trap decay spectroscopy for 2�ͦ¦� decay experiments

Knowledge of 2??|? nuclear matrix elements is essential to probe the theoretical framework of 0??|? decays. At TITAN, TRIUMF??s Ion Trap for Atomic and Nuclear science, a novel technique has been developed to measure electron capture branches of virtual intermediate nuclei in ?|? decays. During two experiments with radioactive ^{124, 126}Cs isotopes the feasibility of this new method was proven.     

Decay of matrix coefficients on reductive homogeneous spaces of spherical type

Let \(Z\) be a homogeneous space \(Z=G/H\) of a real reductive Lie group \(G\) with a reductive subgroup \(H\) . The investigation concerns the quantitative decay of matrix coefficients on \(Z\) under the assumption that \(Z\) is of spherical type, that is, minimal parabolic subgroups have open orbits on \(Z\) .     

An energy-entropy-consistent time stepping scheme for finite thermo-viscoelasticity

This paper presents a time integrator, which is based on a time discrete spatially weak finite element formulation, but fulfills the same balance laws as the underlying (five) differential equations. Namely, in addition to the balances of linear and angular momentum as well as entropy, also the balances of total energy and LYAPUNOV function are fulfilled. The spatially weak formulation is obtained by integration by parts. Where the resulting virtual stress power term is well-known, the virtual entropy production by conduction of heat is less known. The time discretisation is based on the midpoint rule and non-standard time discrete differential operators. This time integrator is a further development of the TC integrator of I. ROMERO. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bicomplex Analogue of Zalcman Lemma

In this paper a bicomplex analogue of Zalcman’s heuristic principle on normal families of meromorphic functions is obtained and as an application a bicomplex version of Lappan’s five-point theorem is proved.