Experimental and theoretical study ofα–Eu₂(MoO₄)₃under compression

Abstract

The compression process in the α-phase of europium trimolybdate was revised employing several experimental techniques. X-ray diffraction (using synchrotron and laboratory radiation sources), Raman scattering and photoluminescence experiments were performed up to a maximum pressure of 21 GPa. In addition, the crystal structure and Raman mode frequencies have been studied by means of first-principles density functional based methods. Results suggest that the compression process of α-Eu2(MoO4)3 can be described by three stages. Below 8 GPa, the α-phase suffers an isotropic contraction of the crystal structure. Between 8 and 12 GPa, the compound undergoes an anisotropic compression due to distortion and rotation of the MoO4 tetrahedra. At pressures above 12 GPa, the amorphization process starts without any previous occurrence of a crystalline-crystalline phase transition in the whole range of pressure. This behavior clearly differs from the process of compression and amorphization in trimolybdates with [Formula: see text]-phase and tritungstates with α-phase.

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

“…As it is known, low-temperature monoclinic α-Eu 2 (MoO 4 ) 3 , space group C 2/ c , is a stable polymorphous modification at room conditions and it can be taken as a representative crystal containing Eu 3+ ions. − Thus, in the present study, α-Eu 2 (MoO 4 ) 3 molybdate is synthesized and their electronic structure is explored by X-ray photoelectron spectroscopy (XPS) and theoretical methods. It should be pointed that in the α-Eu 2 (MoO 4 ) 3 structure the europium ions are in the position with symmetry C 1 and this avoids symmetrical constraints on the electronic parameters of Eu 3+ ions.…”

Role of rare earth sites and vacancies in the anomalous compression of modulated scheelite tungstates RE2 ( WO4)3

“…Among trimolybdates, more studies have been conducted to investigate the compression of the β phase than for the α phase. To our knowledge the following molybdates with α phase are the only ones studied up to now: Nd 2 (MoO 4 ) 3 , Tb 2 (MoO 4 ) 3 [19,20], and Eu 2 (MoO 4 ) 3 [21,22]. The only tungstate studied under high pressure is La 2 (WO 4 ) 3 , which undergoes two distinguishable phase transitions at high pressure compatible with the results of first-principles calculations [23].…”

Revealing the spin-polarized optical properties of monoclinic α-Eu2(MoO4)3: a DFT + U approach

“…More details regarding the use of different values of U are found elsewhere. 38 The potential for the construction of the basis functions inside the sphere of the muffin-tin was spherically symmetric, whereas it was constant outside the sphere. Self-consistency is obtained using 300 k .…”

“…As it is known, low-temperature monoclinic a-Eu 2 (MoO 4 ) 3 , space group C2/c, is a stable polymorphous modication at room conditions and it can be taken as a representative crystal containing Eu 3+ ions. [25][26][27] It should be pointed that, in the a-Eu 2 (MoO 4 ) 3 structure, the europium atoms are in the position with symmetry C 1 , and this avoids symmetrical constrains on the electronic parameters of Eu 3+ ions.…”