First-principles study of pressure-induced structural phase transitions in MnF2
S López-Moreno1, A H Romero2, J Mejía-López3
1CONACYT - Centre for Corrosion Research, Autonomous University of Campeche, Av. Héroe de Nacozari 480, Campeche 24070, Mexico. sinlopez@uacam.mx.
Physical Chemistry Chemical Physics : PCCP
|November 30, 2016
Summary
This study reveals the pressure-induced structural phase transitions in manganese difluoride (MnF2). Calculations predict a specific sequence of phase changes under varying pressure conditions, impacting its magnetic and vibrational properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Materials Science
Background:
- Manganese difluoride (MnF2) is an important material with complex magnetic and structural properties.
- Understanding its behavior under pressure is crucial for predicting its performance in extreme conditions.
- Previous studies on related materials provide a basis for investigating MnF2's high-pressure phases.
Purpose of the Study:
- To perform a comprehensive structural and magnetic characterization of crystalline MnF2 under pressure.
- To elucidate the pressure-driven structural phase transition pathway in MnF2.
- To investigate the influence of hydrostatic and non-hydrostatic conditions on these transitions.
Main Methods:
- First-principles calculations based on Density Functional Theory (DFT) with the generalized gradient approximation plus the Hubbard formalism (GGA+U).
- Quasi-harmonic approximation (QHA) to calculate free energy and determine structural transitions at 300 K.
- Consideration of ten candidate structures for high-pressure regimes, including hydrostatic and non-hydrostatic strains.
Main Results:
- A detailed sequence of pressure-induced structural phase transitions for MnF2 was determined: rutile → α-PbO2-type → dist. HP PdF2-type → dist. fluorite → cotunnite.
- The proposed transition path correlates with observed phase transitions in other metal rutile fluorides.
- The study explains variations in experimental transition paths by accounting for hydrostatic conditions.
Conclusions:
- The calculated structural phase transition sequence provides a theoretical framework for understanding MnF2's high-pressure behavior.
- The findings highlight the critical role of pressure and hydrostatic conditions in modifying MnF2's structural, electronic, and magnetic properties.
- This work offers insights into the fundamental physics governing transition metal difluorides under extreme conditions.
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