title: Polymerization of formic acid under high pressure.
abstract: We report Raman, infrared, and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid (FA) under pressure up to 50 GPa. We find an infinite chain Pna2(1) structure to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intrachain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of long-range order at pressures above 40 GPa, with a large hysteresis upon decompression. We attribute this behavior to a three-dimensional polymerization of FA.
authors.affiliation: Lawrence Livermore National Laboratory, University of California, Livermore, California 94551, USA.
authors.forename: Alexander F
authors.initials: AF
authors.lastname: Goncharov
authors.forename: M Riad
authors.initials: MR
authors.lastname: Manaa
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zaug
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gee
authors.forename: Laurence E
authors.initials: LE
authors.lastname: Fried
authors.forename: Wren B
authors.initials: WB
authors.lastname: Montgomery