Dresden 2026 – scientific programme

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FM: Fachverband Funktionsmaterialien

FM 10: Crystal Defects and Real Structure Physics in Diamond and Functional Materials II

FM 10.1: Talk

Tuesday, March 10, 2026, 14:00–14:15, BEY/0E40

Identification of defects in iron molybdate catalysts via first principles calculations — •Young-Joon Song and Roser Valentí — Institut für Theoretische Physik, Goethe-Universität, 60438, Frankfurt am Main, Germany

Iron molybdate (Fe₂(MoO₄)₃) is well known as a commercial catalyst for oxidative dehydrogenation. Recently, L. Schumacher et al. reported an experimental reduction in Raman intensity at 782 cm⁻¹ during catalytic processes. The authors attribute this decrease to oxygen migration from the bulk to the surface during the reaction, in contrast to the conventional understanding that oxygen atoms are supplied only near the surface. To identify the types of defects responsible for the observed reduction in Raman intensity, we performed DFT electronic and phononic structure calculations for Fe₂(MoO₄)₃. Our findings reveal that optical phonon modes involving oxygen dominate the spectrum at around 790 cm⁻¹, with a small contribution from Mo, corresponding to asymmetric MoO₄ stretching modes. In the Raman calculations, a major peak appears at 789.68 cm⁻¹ with a small shoulder-like feature and a minor peak at 972.05 cm⁻¹, consistent with the experimental observations. By selectively freezing specific phonon modes, we introduced an effective method to incorporate defect effects into Raman calculations without explicitly creating oxygen vacancies. Using this approach, we found that oxygen vacancies play a dominant role in the reduction of Raman intensity. Finally, we discuss the relaxed structure containing explicit oxygen vacancies. This research was supported by the German Research Foundation for funding through CRC 1487.

Keywords: oxygen defects; Raman intensity calculation; phonon calculation; catalysis; iron molybdate