Study on Enhancing the Thermoelectric Properties of Ti2CrSn Alloys

Based on the Hg2CuTi structure, the full-Heusler alloy Ti2CrSn, with a ground state band gap of semiconductor, is a thermoelectric material with potential applications. Through preparing Ti2CrSn1−xAlx (x = 0, 0.05, 0.1, 0.15, 0.2) series bulk materials via arc melting, the effects of the electrical and thermal transport properties of Ti2CrSn series alloys were investigated, and different Al doping on the phase structure, the microscopic morphology, and the thermoelectric properties of Ti2CrSn were examined. The results show that the materials all exhibit characteristics of p-type semiconductors at the temperature range of 323 to 923 K. Al elemental doping can significantly increase the Seebeck coefficient and reduce the thermal conductivity of the materials. Among them, the sample Ti2CrSn0.8Al0.2 obtained a maximum value of 5.03 × 10−3 for the thermoelectric optimal ZT value at 723 K, which is 3.6 times higher than that of Ti2CrSn.

Calculation of Nuclear Properties for 56–62Fe Isotopes in the Model Space (HO) Using NuShellX@MSU Code

The nuclear shell model has been applied to calculate the yrast energy levels, quadrupole transition probability (BE2), deformation parameter B2, rotational energy (hw), and inertia moment (20/h2) for the ground state band. The NuShellX@MSU code has been used to determine the nuclear properties of 56−62Fe isotopes, by using the harmonic oscillator (HO) model space for P (1f7/2), N (2p3/2), N (1f5/2), and N (2p1/2) orbits and (HO) interaction. The results are in good agreement with the available experimental data on the above nuclear properties and all nuclei under study. In addition, the back bending phenomenon has been explained by the calculations, and it has been very clear in 58,60,62Fe nuclei. It has also been confirmed and determined the most spins and parities of energy levels. In these calculations, new values have been theoretically determined for the most nuclear properties which were previously experimentally unknown.

Partial alpha-decay half-life of 178Hfm2 isomer

A simple, semi-empirical, one-parameter calculation model based on the quantum mechanical tunneling mechanism through a potential barrier has been used to estimate the partial [Formula: see text]-decay half-life, [Formula: see text], of [Formula: see text] isomer. Alpha-transitions to levels of the ground-state band [Formula: see text] of [Formula: see text] have been considered, and the contributions to [Formula: see text] due to overlapping, Coulomb, and centrifugal barriers have been detailed in each case. Results have indicated a [Formula: see text]-value of [Formula: see text] and a predominance [Formula: see text] of [Formula: see text]-particles populating the level [Formula: see text], compatible with results by other authors. Besides, a single, universal-like formula to estimate half-life of alpha transitions, whatever [Formula: see text]-value and the characteristics of the parent nucleus (e-e, e-o, o-e and o-o nuclei, whether in the ground or isomeric states), has been envisaged.

Variational procedure leading from Davidson potentials to the E(5)and X(5) critical point symmetries

Davidson potentials of the form β^2 + β0^4/β^2, when used in the original Bohr Hamiltonian for γ-independent potentials bridge the U(5) and 0(6) symmetries. Using a variational procedure, we determine for each value of angular momentum L the value of β0 at which the derivative of the energy ratio RL = E(L)/E(2) with respect to β0 has a sharp maximum, the collection of RL values at these points forming a band which practically coincides with the ground state band of the E(5) model, corresponding to the critical point in the shape phase transition from U(5) to Ο(6). The same potentials, when used in the Bohr Hamiltonian after separating variables as in the X(5) model, bridge the U(5) and SU(3) symmetries, the same variational procedure leading to a band which practically coincides with the ground state band of the X(5) model, corresponding to the critical point of the U(5) to SU(3) shape phase transition. A new derivation of the Holmberg-Lipas formula for nuclear energy spectra is obtained as a by-product.

W(5): Wobbling Mode in the Framework of the X(5) Model

Using in the Bohr Hamiltonian the approximations leading to the Bohr and Mot- telson description of wobbling motion in even nuclei, a W(5) model for wobbling bands, coexisting with a X(5) ground state band, is obtained. Separation of vari­ ables is achieved by assuming that the relevant potential has a sharp minimum at 70, which is the only parameter entering in the spectra and B(E2) transition rates (up to overall scale factors). B(E2) transition rates exhibit the features expected in the wobbling case.

γ-rigid solution of the Bohr Hamiltonian compared to the E(5) critical point symmetry

A γ-rigid solution of the Bohr Hamiltonian for 7 = 30° is derived, its ground state band being related to the second order Casimir operator of the Euclidean algebra E(4). Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are in close agreement to the E (5) critical point symmetry, as well as to experimental data in the Xe region around A = 130.

g-factors of some excited states in 49,50Cr

Magnetic moments of the first excited states in 50Cr and of the 7/2" and 19/2' states in 49Cr, have been measured by the transient field technique. The states were excited by the inverse reaction 40Ca + 12C and the recoil nuclei traversed a thick gadolinium foil. The observed rotations, of the 2+, 4+, 6+, 8+ states of the ground-state band in 50Cr, were found into the experimental error to be the same, suggesting similar g-factors for these states and thus supporting a high collectivity for the ground-state band, g-factors of the 7/2' and 19/2 states in 49Cr, were deduced by adopting both an overall parametrization of the transient magnetic field in Gd and by comparing the 49Cr rotations with rotations of states with known magnetic moments, as the 2+ ones of 50Cr and of 46Ti which was also populated in the same reaction. Both methods gave similar results and the g-factors adopted for the 19/2" and 7/2" states were + 0.78(17) and +0.35(7) respectively. These results are discussed in terms of cranked shell model calculations and are found to support a proton alignment in the f7/2 shell.

Analytic description of critical point actinides in a transition from octupole deformation to octupole vibrations

An analytic collective model in which the relative presence of the quadrupole and octupole deformations is determined by a parameter (φο), while axial symmetry is obeyed, is developed. The model [to be called the analytic quadrupole octupole axially symmetric model (AQOA)] involves an infinite well potential, provides predictions for energy and Β (EL) ratios which depend only on φο, draws the border between the regions of octupole deformation and octupole vibrations in an essentially parameter-independent way, and describes well 2 2 6Th and 226Ra, for which experimental energy data are shown to suggest that they lie close to this border. The similarity of the AQOA results with φο = 45° for ground state band spectra and B(E2) transition rates to the predictions of the X(5) model is pointed out.