Influence of temperature on the process of hydrogen bond symmetrization in ε-FeOOH

ZS Lei and XW Sun and XX Wang and ZJ Liu and T Song and JH Tian, PHYSICAL REVIEW B, 108, 184105 (2023).

DOI: 10.1103/PhysRevB.108.184105

Investigating hydrogen bond symmetrization in hydroxyl compounds necessitates the precise determination of crystal microstructures. Nonetheless, H atoms are nearly indistinguishable in experiments, posing a challenge to unraveling the formation mechanism of this phenomenon. A deep learning potential model was used for classical molecular dynamics simulations of the hydrogen bond symmetrization process of epsilon-FeOOH in this study. Through calculations of the H-O bond length, it has been determined that the system undergoes hydrogen bond symmetrization when the pressure reaches 40.25 GPa. The volume thermal expansion curve of epsilon-FeOOH exhibits anomalies due to the proton-disordering phase transition, and the pressure for this transition shows a negative correlation with temperature. The calculated results of the O-1 center dot center dot center dot O-2 bond length indicate that an increase in temperature will lead to an increase in the critical pressure for hydrogen bond symmetrization while reducing the distinction between the hydrogen bond symmetrization structure and the proton-disordered structure. In addition, the spin transition of Fe atoms at lower temperatures is unrelated to hydrogen bond symmetrization. However, with increasing temperature, the spin transition may potentially promote hydrogen bond symmetrization.

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