With the ongoing effort to obtain mononuclear 3d-transitionmetal complexes that manifest slow relaxation of magnetization and, hence, can behave as single-molecule magnets (SMMs), we have modeled 14 Fe(III) complexes based on an experimentally synthesized (PMe 3 ) 2 FeCl 3 complex [J. Am. Chem. Soc. 2017, 139 (46), 16474−16477], by varying the axial ligands with group XV elements (N, P, and As) and equatorial halide ligands from F, Cl, Br, and I. Out of these, nine complexes possess large zero field splitting (ZFS) parameter D in the range of −40 to −60 cm −1 . The first-principles investigation of the ground-spin state applying density functional theory (DFT) and wave function-based multiconfigurations methods, e.g., SA-CASSCF/NEVPT2, are found to be quite consistent except for few delicate cases with near-degenerate spin states. In such cases, the hybrid B3LYP functional is found to be biased toward high-spin (HS) state. Altering the percentage of exact exchange admixed in the B3LYP functional leads to intermediate-spin (IS) ground state consistent with the multireference calculations. The origin of large zero field splitting (ZFS) in the Fe(III)-based trigonal bipyramidal (TBP) complexes is investigated. Furthermore, a number of complexes are identified with very small ΔG HS−IS adia. values indicating the possible spin-crossover phenomenon between the bistable spin states.

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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.

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Multiphoton absorption processes have been studied theoretically. It has been shown that the processes above five-photon absorption do not occur in the hydrocarbons using the present available laser power. It has been further shown that different input laser energy is needed to induce different process orders. The limits for various process orders have been estimated, along with the process emission wavelengths. Theoretical expressions have been derived which completely explain the experimental results using Feynman diagrams. The discrepancy noted by Pantell et al (1967) between their theoretical and experimental results has been discussed. The difference between the emission and the absorption frequencies in various process orders has been explained using the above diagrams. Spin analysis has been used to calculate the nature of the final state, the polarization of fluorescence, and the wavefunction. The results have been verified using spin analysis, dipole moment concepts, and Huckel's theory.