Simulation of crystal and electronic structures of octahedral molybdenum cluster complex compound Cs₂[Mo₆Cl₁₄] using various DFT functionals

Abstract

The electronic and structural characteristics of the octahedral molybdenum cluster-based ternary compound, Cs 2 [Mo 6 Cl 14 ], were investigated based on density functional theory (DFT) and subsequent comparisons with experimentally observed results. The geometry optimization and band structure calculations of Cs 2 [Mo 6 Cl 14 ] were performed using three standard functionals: local density approximation, Perdew-Burke-Ernzerhof (PBE) as a generalized gradient approximation, and PBE revised for solid compounds (PBEsol). The validity of the calculated results was experimentally examined via X-ray powder diffraction, ultraviolet visible (UVvis) diffuse reflection, and X-ray photoemission spectra (XPS) measurements. PBEsol was found to show the best performance in terms of reproducing the experimentally refined lattice structure of the compound. The calculated band gap energy (E g ) was consistent with the value evaluated from the UVvis measurement. Furthermore, the XPS valence spectrum of the compound was well reproduced by the calculated projected density of state weighted with the photoionization probabilities of Al K ¡ . Although the spectral shapes simulated using the three functionals were similar, PBEsol reproduced the energy levels of the electronic states of both [Mo 6 Cl 14 ] 2¹ and Cs + ion with greater consistency. Therefore, it was concluded that PBEsol is the most appropriate functional for DFT calculations of the metal cluster-based lattice system.

Octahedral Molybdenum Cluster-Based Single Crystals as Fabry–Pérot Microresonators

“…These clusters have outstanding optical properties such as absorption of light in the UV–vis range, bright emission in the red/near-IR region with high quantum yields, and PL lifetimes up to several hundreds of microseconds. − It is also well-known that these clusters act as efficient photosensitizers in processes related to the generation of singlet oxygen. These properties make these inorganic compounds particularly attractive in design of functional hybrid nanomaterials with potential applications in nanoarchitectonics, , optoelectronics, − lighting, hydrogen storage, biomedicine, ,− and catalysis. − Surprisingly, only scarce studies about the optical and electronic properties of octahedral molybdenum cluster-based materials at the single crystal level and at the micrometer scale are reported, and those are limited to Cs 2 [Mo 6 X i 8 X a 6 ] (X = Cl, Br, I) compounds. − …”