We study here the ternary-fission mass distribution of the 252 Cf nucleus for a fixed third fragment 48 Ca using the level-density approach within the framework of statistical theory. For the evaluation of nuclear level densities, the single-particle energies of the finite-range droplet model are used. Our results for temperatures T = 1 and 2 MeV reproduce qualitatively the experimental expectation of ternary fragmentation of 132 Sn + 72 Ni + 48 Ca. In addition, different possible ternary-fission modes are highlighted.

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A systematic study on the room temperature ferromagnetism (RTFM) in undoped and Mn-doped ZnO nanoparticles (NPs) prepared by the coprecipitation method has been reported. The neutral and singly ionized zinc vacancy defects exhibited in the results of photoluminescence (PL), micro-Raman spectroscopy, and electron paramagnetic resonance (EPR) studies are found to be of ferromagnetic origin in bare ZnO, and it has been confirmed that Mn2+ ions substitutionally enter at Zn2+ sites in wurtzite ZnO. The results of positron annihilation and coincidence Doppler broadening measurements corroborate the Zn vacancies and their clusters. It is observed that in Mn:ZnO, the magnetic ordering is changed from ferro- to paramagnetic because of interacting adjacent Mn–Mn ions. The higher saturation magnetization of 565 × 10–3 emu/g is explained by a quasi indirect exchange mechanism based on the interaction of bound magnetic polarons formed by the Zn vacancies (V Zn) and nearby Mn ions. Further, first principle calculations reveal the magnetic centers in nonmagnetic ZnO with V Zn and the stable ferromagnetic ordering in Mn:ZnO at the optimum distance of Mn–Mn ≈ 3.26 Å.

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In this Letter, we report on the role of Se incorporation in the increased efficiency recently measured in Se alloyed cadmium telluride (CdTe) absorbers. This is done by means of density functional theory calculations following an extensive exploration of all the possible diffusion paths of Se. We identify a unique two-step mechanism that accounts for bulk diffusion of chalcogenide interstitials in CdTe, explaining the Se diffusion measured in experiments. The interaction of the diffusing interstitial with the Cd vacancy and the Te antisite is further analyzed in order to understand the passivation of these two main non-radiative recombination centers. Taking into account the approach path of Se, we identify nine complexes that present different levels of passivation. The lowest formation energy is achieved for a ⟨100⟩ Te dimer with two Se in the first neighbor shell. This defect also presents the shallowest donor character defect state due to the presence of Se. This highlights the hybrid role of Se in the mechanism of increased efficiency: it first mediates the diffusion of chalcogenide toward the non-radiative recombination centers before it leads with Te to their optimal passivation. This comprehensive insight should allow further improvements in CdTe-based technologies.