The Low-Temperature Vibrational Behavior of Pentaerythritol Tetranitrate

Abstract

Approved for public release; distribution is unlimited.ii REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)June 2008 ARL-TR-4470 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES* Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015 ABSTRACTThe authors report the room temperature Raman and synchrotron Fourier transform infrared measurements of pentaerythritol tetranitrate (PETN), as well as low-temperature Raman measurements from 4 to 298 K up to ~15 GPa, using a helium gaspressure medium. No evidence of phase transitions was observed in the pressure/temperature range studied, although the molecular symmetry of PETN is modified from S4 to D2 near 8.1 GPa. The modification was not found to be temperature dependent, and decompression studies indicated the reversibility of the symmetry change. SUBJECT TERMSvibrational spectroscopy, high pressure, pentaerythritol tetranitrate, diamond anvil cell, PETN

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“…When compressed at room temperature (298 K), PETN shows a change in the molecular symmetry from S 4 → D 2 between 6.3 and 10.9 GPa (figures 2 and 3). The exact pressure of the symmetry transformation is known to be strongly dependent on the conditions within the cell as well as the crystalline phase (i.e., powder or single crystal) (27), but in this work, the transition pressure was near 8.1 GPa. The transformation can be visually observed since single-crystal PETN normally appears translucent, but after the transformation, the sample looks slightly opaque.…”

“…Under hydrostatic conditions with nearly no sample strain, the modifications in the vibrational spectra indicated a symmetry change to the D 2 molecular geometry, but no crystallographic phase transition was observed between ambient pressure and 14 GPa. Several less hydrostatic samples with a higher degree of stress/strain showed a significant loss of vibrational resolution in both the number of visible peaks and intensity, presumably due to the activation of the PETN slip planes (27). The loss of intensity, coupled with the disappearance of several vibrational peaks, may have been misconstrued as a phase transition (27).…”

“…Several less hydrostatic samples with a higher degree of stress/strain showed a significant loss of vibrational resolution in both the number of visible peaks and intensity, presumably due to the activation of the PETN slip planes (27). The loss of intensity, coupled with the disappearance of several vibrational peaks, may have been misconstrued as a phase transition (27).…”

Modeling solid–solid phase transitions in PETN using density functional theory

“…They also observed changes in Raman spectra of single-crystal PETN using N 2 , Ne, and He as pressure media, but found that the threshold pressures varied significantly with the pressure medium [9]. They concluded that the appearance of the new phase is correlated with the onset of non-hydrostatic response of the pressure medium.…”

“…Ciezak and Jenkins [9] observed peak splittings between 6 and 9 GPa in Raman spectra of PETN powder using Ne as a pressure medium. They also observed changes in Raman spectra of single-crystal PETN using N 2 , Ne, and He as pressure media, but found that the threshold pressures varied significantly with the pressure medium [9].…”