Development of novel softwares for multiplet calculation

In the ligand-field science, the multiplet structures of the transition-metal ions or rare-earth ions play important roles. The multiplet structures are generally analyzed based on the crystal-field theory or the ligand-field theory. However, since they are semi-empirical approaches where the values of parameters are determined based on the experimental results, they cannot be applied to the analysis of the unknown or fictitious materials. In this laboratory, a unique first-principles electronic structure calculation software for multiplet calculation without empirical parameters (Discrete-Variational Multi-Electron;DVME program) was developed. This enables one to predict and analyze the electronic structures and the spectra of unknown or fictitious materials.

Ligand-field science based on first-principles calculation

@In the crystal-field theory and the ligand-field theory, the values of parameters are generally determined based on the experimental results. In these approaches, however, the spectra cannot be connected to the corresponding local structure such as bond lengths or bond angles. In contrast, since the first-principles calculations using the DVME code are performed using the model clusters representing the local structure, the correspondence between the local structure and the spectra can be clarified. In addition, the effects of covalency, iconicity, crystal field, etc. are absorbed in the values of parameters and no longer separable in the ordinary analysis. However, these effects can be separated and analyzed quantitatively in the analysis based on the first-principles calculation. Therefore, more detailed analysis can be performed.

Electronic structure analysis of phosphors / solid state lasers

@Transition-metal ions or rare-earth ions are utilized as luminescent ions in phosphors or solid state lasers. Since white LEDs are recently drawing attention as next-generation lighting source, the importance of phosphors for white LED is increasing. We explore the design guidelines of the luminescent materials with improved properties based on the detailed analysis of the multiplet structures of transition-metal ions or rare-earth ions using the DVME code.