Ab Initio Structure Determination of La₃₄Mo₈O₇₅ Using Powder X-ray and Neutron Diffraction Data

Abstract

We report the synthesis, the structure determination, and the structure analysis of La34Mo8O75, which comprises 68 mol % La2O3 in the binary system La2O3–MoO3, in place of the previously reported compound La4MoO9, 66.7 mol % La2O3. This latter compound, which was reported in the literature without any structural information, is presented in this Article as part of the exploration of the La2O3–Nb2O5–MoO3 ternary phase diagram. Several diffraction techniques were used for the structural resolution of this compound such as powder X-ray and neutron diffraction as well as transmission electron microscopy in diffraction mode. La34Mo8O75 crystallizes in the monoclinic space group C2/m with the cell parameters: a = 17.070 Å, b = 12.204 Å, c = 9.742 Å, β = 109.58°. The structure, related to fluorite, can be described as an anion-deficient fluorite with the global formula La34Mo8O75□9. The oxygen conduction of the compound was also investigated by means of complex impedance spectroscopy.

Unravelling Crystal Superstructures and Transformations in the La6–xMoO12−δ (0.6 ≤ x ≤ 3.0) Series: A System with Tailored Ionic/Electronic Conductivity

“…Different phases are identified, including R1, R2, and La 2 O 3 , a similar behavior to that previously observed for La 5.4 MoO 11.1 . 21 In the case of La 4.5 T-5 in the 1000−1300 °C temperature range, mixtures of a cubic fluorite (isostructural with PDF 00− 024−1087), R2, La 2 MoO 6 (PDF 01−080−0437), and the monoclinic phase, 31 with composition La 34 Mo 8 O 75, were identified (Figure 1b). At higher temperatures, i.e., T ≥ 1400 °C, single phases with a cubic symmetry were obtained.…”

Morphology and Study the Crystal Chemistry of a Novel Ternary Mixed Valence Bi1.52 Co2.52 Zr0.751 N0.641 O8.12 Oxide Orthorhomic Crystal Structure by Ab Initio Method via Powder XRD

“…The sample is then scanned with a focused fine beam of electrons. The surface characteristics of the sample are obtained from the secondary electrons emitted [12] from the sample surface. The morphology of the oxide nanoparticles is shown in Fig-2.…”

“…In particular, the non-kinematical nature of the diffracted intensities is a great concern for structure analysis with electron diffraction data and has hindered EDSA from becoming very popular since its foundation in Russia more than 65 years ago. While a large number of lightatom structures have been investigated by electron diffraction in the past [1][2][3][4], it has only succeeded in a few cases to solve structures with heavier atoms directly from X-ray diffraction spot patterns. In order to avoid these problems, an alternative approach was developed for such non-light-atom structures.…”

“…As mentioned earlier, the non-kinematical (dynamical) nature of the electron intensities is the main concern in this endeavour because its influence on the diffracted intensities is very difficult to control in the diffraction experiment. However, today it is generally believed that the precession electron diffraction method, developed in the early 1990s by Vincent and Midgley [12], is the most promising way out from this quandary. In the precession method, a small focussed or parallel electron beam is scanned at a constant angle around the optic axis to produce a hollow-cone illumination of the sample.…”

Synthesis and ab initio Determination of Bi1.25 V0.123 Ca 0.245 N1.24 O8 cubic structure via powder X-ray diffraction data

“…Pn-3n (222). The initial structure model was obtained using a charge flipping algorithm with the program Superflip 8 [11]. Random phases were used at the beginning of the charge-flipping interaction, and overlapping peaks were repartitioned using a histogram match to improve the convergence.…”