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Ligand-induced chirality in semiconducting nanocrystals has been the subject of extensive study in the past few years and shows potential applications in optics and biology. Yet, the origin of the chiroptical effect in semiconductor nanoparticles is still not fully understood. Here, we examine the effect of the interaction with amino acids on both the fluorescence and the optical activity of chiral semiconductor quantum dots (QDs). A significant fluorescence enhancement is observed for l/d-Cys-CdTe QDs upon interaction with all the tested amino acids, indicating suppression of nonradiative pathways as well as the passivation of surface trap sites brought via the interaction of the amino group with the CdTe QDs’ surface. Heterochiral amino acids are shown to weaken the circular dichroism (CD) signal, which may be attributed to a different binding configuration of cysteine molecules on the QDs’ surface. Furthermore, a red shift of both CD and fluorescence signals in l/d-Cys-CdTe QDs is only observed upon adding cysteine, while other tested amino acids do not exhibit such an effect. We speculate that the thiol group induces orbital hybridization of the highest occupied molecular orbital (HOMOs) of cysteine and the valence band of CdTe QDs, leading to the decrease of the energy band gap and a concomitant red shift of CD and fluorescence spectra. This is further verified by density functional theory calculations. Both the experimental and theoretical findings indicate that the addition of ligands that do not “directly” interact with the valence band (VB) of the QD (noncysteine moieties) changes the QD photophysical properties, as it probably modifies the way cysteine is bound to the surface. Hence, we conclude that it is not only the chemistry of the amino acid ligand that affects both CD and PL but also the exact geometry of binding that modifies these properties. Understanding the relationship between the QD’s surface and chiral amino acid thus provides an additional perspective on the fundamental origin of induced chiroptical effects in semiconductor nanoparticles, potentially enabling us to optimize the design of chiral semiconductor QDs for chiroptic applications.

The electronic and optical properties of hybrid perovskites CH3NH3SnX3 (X = Br, I) are investigated by first-principles calculations. Our results show that consideration of the weak van der Waals interactions is important for theoretical investigations of Sn-based hybrid materials. During light harvesting, the electron transition will occur between the p states of halogen at the valence band maximum (VBM) and the Sn 5p states at the conduction band minimum (CBM). Comparing with the energy distribution of solar spectra, CH3NH3SnI3 has better absorption characteristics in the visible region than CH3NH3PbI3, which shows promising prospects in realizing lead-free, highly efficient solar cells.

The electronic structure of heavy fermion superconductor CeMIn5 (M=Co,Rh,Ir) is studied by density functional theory. Our results indicate that the MIn2 layer plays an important role for stabilizing the layered crystal structure and determining the antiferromagnetic or paramagnetic ground state in this series. When the strong correlation effects of 4f electrons beyond the local density approximation (LDA) are taken into account by the LDA+U approach, the calculated total magnetic moment and band structure of CeRhIn5 yield a good agreement with the experiment. The LDA+U calculation shows that the 4f electrons in this series are located on the border between localization and itineracy.

First-principles calculations were performed to investigate the pressure induced phase transition in SrRuO3 and to compare electronic structures and magnetism of A RuO3 (A= Ca, Sr, and Ba). By combining with the substitutions of Ca(Ba) for Sr in SrRuO3, ferromagnetism evolutions and its origin in A RuO3 are caused by the structural transition induced by the A2+ ionic size. On the (Sr,Ba)RuO3 side, the band broadening induced the decrease of electron–electron exchange interaction is a main reason, while on the (Sr and Ca) RuO3 side, spin–orbital coupling effect and magnetic instability suppress the ferromagnetism.

The electronic structures and magnetic properties induced by the substitution of Mg in MgCNi3 were investigated by performing the first-principles density functional calculations. It is confirmed that AlCNi3, GaCNi3, and InCNi3 are paramagnetic nonsuperconductors resulting from total energy, density of states at Fermi level, and electron-phonon coupling constant. A large peak of density of states lies on the Fermi level, resulting in ferromagnetism rather than superconductivity in NaCNi3. The substitution of dual elements for Mg, such as Al0.5Na0.5CNi3 and Al0.5Li0.5CNi3, was inspected too. Evaluating the electron-phonon coupling interaction, the possible superconductivity exists in near ferromagnetic Al0.5Na0.5CNi3.

The band structure, Fermi surface, and generalized susceptibility χ(q) in the constant-matrix-element approximation for the heavy fermion series CeIn3, CeMIn5(M=Co,Rh,Ir), and PuCoGa5 are studied by density functional calculations to address the relationship among superconductivity, magnetism, and Fermi surface nesting in these compounds. Within the scenario of magnetically mediated d wave superconductivity, our results indicate that the behavior of χ(q) of the Ce class materials favors superconductivity if 4f electrons are treated as core states, since it exhibits broad plateaus with large magnitude around q=(0.5,0.5,0) and (0.5, 0.5, 0.5). In contrast, when the 5f electrons are treated as valence electrons, the χ(q) of PuCoGa5 exhibits a very sharp peak at q=(0.5,0.5,0) due to the strong nesting of hole and electron Fermi surface from the 16th and 17th bands. Not only the large spin fluctuation energy but also the strong nesting of Fermi surface in PuCoGa5 may contribute to the much higher Tc than that ...

The effects on the electronic structure and magnetic property of the Ni site substitution in nonoxide perovskite superconductor MgCNi3 are studied by using density functional calculations. A sharp high peak of Ni d density of states just lies below the Fermi energy in pure MgCNi3. Co-doping results in the onset of ferromagnetism at x=0.083. However, the little energy gain as well as small magnetic moment per atom indicate the weak itinerant ferromagnetism. The strong ferromagnetic spin fluctuation in MgCNi3−xCox leads to quench bulk superconductivity, while the Mn atom forms a local magnetic moment of 1.06 μB at x=0.042 which suppresses superconductivity more seriously than Co does in the low doping case. Cu doping can be well accounted for by the rigid band model, which reduces the density of states at the Fermi level and the Tc.