Exploration of the Electronic Structure of Monoclinic α-Eu₂(MoO₄)₃: DFT-Based Study and X-ray Photoelectron Spectroscopy

Abstract

The powder α-Eu 2 (MoO 4 ) 3 sample was prepared by the solid-state reaction method. The phase purity of the final powder product was verified by X-ray diffraction analysis. The constituent element core levels and valence band are measured by X-ray photoelectron spectroscopy as a function of Ar + ion (2.5 keV, 7−8 μA/cm 2 ) bombardment time. The formation of Mo 5+ and Mo 4+ states at high bombardment times was detected. The Eu−O and Mo−O bonding was considered in comparison with other Eu 3+ -and Mo 6+ -containing oxides using binding energy difference parameters. The transparency range obtained for the pure α-Eu 2 (MoO 4 ) 3 tablet is λ = 0.41−0.97 μm, as estimated at the transmission level of 5%. The short-wavelength cut edge in α-Eu 2 (MoO 4 ) 3 is governed by the direct allowed optical transitions within the band gap of E g = 3.74 eV (300 K). The band structure of α-Eu 2 (MoO 4 ) 3 was calculated by ab initio methods and strongly different results were obtained for the spin up/down configurations. The Eu-4f states are located around 2.2 eV and −4.0 eV for spin up (↑) and the structures situated at around 6.5 and 5.5 eV for spin down (↓) configuration. The calculated spin magnetic moments are in excellent relation to the Slater-Pauling rule and within the Eu sphere the magnetic moment of 4f electrons is ∼5.99 μB.

Exploration of structural, thermal and spectroscopic properties of self-activated sulfate Eu2(SO4)3 with isolated SO4 groups

“…For this reason, in complex compounds, it is difficult to define clearly the relation between the spectroscopic parameters and the Eu 3+ ion coordination in the host lattice. In this situation, the europium compounds, where Eu 3+ is a constituent element, are more suitable for this purpose because the Eu 3+ ion coordination can be precisely defined by the methods of modern crystal structure analysis [27][28][29][30][31][32][33][34]. Thus, the present study is aimed at the synthesis of anhydrous Eu2(SO4)3 and evaluation of their structural and optical properties.…”

Enhanced luminescence and thermal stability of (Sr,Ca)AlSiN3:Eu2+ via superficial organic carbon modification

“…As shown in Figure 7, the regions around ~1,130 and ~1,160 eV are corresponded to Eu 3d 5/2 and Eu 3d 3/2 components, and the two peaks at 1,125.6 and 1,135.6 eV are attributed to Eu 2+ and Eu 3+ ions, respectively. [28][29][30] Through calculation, the proportions of Eu 2+ on the surface of the C2#SCASN:Eu 2+ sample is larger than that of the #SCASN:Eu 2+ sample, but the proportions of Eu 2+ on the surface of the C0#SCASN:Eu 2+ sample is smaller than that of the #SCASN:Eu 2+ sample, as shown in Table 1. It means that the deionized water involved in the whole superficial organic carbon modification processing cannot inhibit the oxidation of activator ion and even cause harm, but the incorporation of carbon achieves a protection effect on reducing the oxidation of Eu 2+ to enhance 8.…”

Phase Transition as an Emergent Phenomenon Analysed by Violation of Structural Invariant (M, BM)

“…For comparison of various interpretation of concepts of emergence and emergent behavior we introduce [10,11,2,4]. The references [7,9,16,17] are introduced as a line to the fields of computational and crystalographic chemistry. Our method of analysis and the detection of emergent situations has been published many times, e.g., in [5,1,3,4].…”