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CaSO4 and its pressure-induced phase transitions. A density functional theory study
Lourdes Gracia1, Armando Beltrán, Daniel Errandonea
1Departament Química Física i Analítica, Universitat Jaume I, 12071 Castelló de la Plana, Spain. lgracia@qfa.uji.es
Inorganic Chemistry
|January 7, 2012
Summary
High-pressure calcium sulfate (CaSO(4)) undergoes structural transitions to monazite-type and barite-type polymorphs. These findings advance understanding of mineral behavior under extreme pressure conditions.
Area of Science:
- Materials Science
- Geophysics
- Computational Chemistry
Background:
- Calcium sulfate (CaSO(4)) exists in various polymorphs.
- Understanding mineral behavior under high pressure is crucial for geophysics.
- Previous studies have explored CaSO(4) phases, but high-pressure transitions require further theoretical investigation.
Purpose of the Study:
- To investigate theoretically the high-pressure polymorphs of calcium sulfate (CaSO(4)).
- To determine the sequence of pressure-driven structural transitions.
- To calculate the equation of state and vibrational properties of different CaSO(4) polymorphs.
Main Methods:
- Density functional theory (DFT) calculations.
- B3LYP hybrid functional for total-energy calculations and geometry optimizations.
- Equation of state determination and vibrational property analysis.
Main Results:
- A pressure-driven transition sequence was identified: anhydrite (Cmcm) → monazite-type (P2(1)/n) at 5 GPa → barite-type (Pnma) and scheelite-type (I4(1)/a) at 8 GPa.
- Equations of state for the identified polymorphs were determined.
- Vibrational properties were calculated and compared with existing data.
Conclusions:
- The study elucidates the high-pressure structural behavior of calcium sulfate.
- Theoretical predictions provide a basis for experimental validation.
- The findings contribute to the understanding of mineral physics under extreme conditions.
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