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Polymerization of formic acid under high pressure
Alexander F Goncharov1, M Riad Manaa, Joseph M Zaug
1Lawrence Livermore National Laboratory, University of California, Livermore, California 94551, USA.
Physical Review Letters
|March 24, 2005
Summary
High-pressure studies reveal formic acid (FA) forms an infinite chain structure. Above 20 GPa, hydrogen bonds gain covalent character, and at 40 GPa, it polymerizes into a disordered 3D network.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Physical Chemistry
Background:
- Formic acid (FA) is the simplest carboxylic acid.
- Understanding its behavior under extreme conditions is crucial for materials science.
Purpose of the Study:
- To investigate the structural and bonding changes in formic acid under high pressure.
- To characterize the high-pressure phases and transitions of FA.
Main Methods:
- Raman spectroscopy
- Infrared spectroscopy
- X-ray diffraction (XRD)
- Ab initio calculations
Main Results:
- Identified a high-pressure phase with an infinite chain Pna2(1) structure.
- Observed hydrogen bond symmetrization and partial covalent character above 20 GPa.
- Detected loss of long-range order and 3D polymerization above 40 GPa, with significant hysteresis.
Conclusions:
- Formic acid undergoes significant structural transformations under pressure.
- The high-pressure phase exhibits unique bonding characteristics.
- Pressure-induced polymerization leads to a disordered state.