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Title: Diffusion on (110) Surface of Molecular Crystal Pentaerythritol Tetranitrate

Abstract

Using classical molecular dynamics simulations, we investigate the diffusion mechanisms of admolecules on the (110) surface of molecular crystal pentaerythritol tetranitrate. Our results show that (1) admolecules are stable at off lattice sites, (2) admolecules diffuse along close-packed [1{bar 1}1] and [{bar 1}11] directions, and (3) admolecules detach from the surface at 350K and above. Based on the number of diffusion jumps as a function of temperature, we estimate the jump frequency to be v=1.14 x 10{sup 12} e{sup -0.08eV/kT} per second.

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
946933
Report Number(s):
UCRL-JRNL-227501
Journal ID: ISSN 0003-6951; APPLAB; TRN: US200904%%337
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters, vol. 90, no. 10, March 5, 2007, pp. 101906; Journal Volume: 90; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUMM MECHANICS, GENERAL PHYSICS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DIFFUSION; MOLECULAR CRYSTALS; PETN

Citation Formats

Wang, J, Golfinopoulos, T, Gee, R H, and Huang, H. Diffusion on (110) Surface of Molecular Crystal Pentaerythritol Tetranitrate. United States: N. p., 2007. Web. doi:10.1063/1.2709955.
Wang, J, Golfinopoulos, T, Gee, R H, & Huang, H. Diffusion on (110) Surface of Molecular Crystal Pentaerythritol Tetranitrate. United States. doi:10.1063/1.2709955.
Wang, J, Golfinopoulos, T, Gee, R H, and Huang, H. Thu . "Diffusion on (110) Surface of Molecular Crystal Pentaerythritol Tetranitrate". United States. doi:10.1063/1.2709955. https://www.osti.gov/servlets/purl/946933.
@article{osti_946933,
title = {Diffusion on (110) Surface of Molecular Crystal Pentaerythritol Tetranitrate},
author = {Wang, J and Golfinopoulos, T and Gee, R H and Huang, H},
abstractNote = {Using classical molecular dynamics simulations, we investigate the diffusion mechanisms of admolecules on the (110) surface of molecular crystal pentaerythritol tetranitrate. Our results show that (1) admolecules are stable at off lattice sites, (2) admolecules diffuse along close-packed [1{bar 1}1] and [{bar 1}11] directions, and (3) admolecules detach from the surface at 350K and above. Based on the number of diffusion jumps as a function of temperature, we estimate the jump frequency to be v=1.14 x 10{sup 12} e{sup -0.08eV/kT} per second.},
doi = {10.1063/1.2709955},
journal = {Applied Physics Letters, vol. 90, no. 10, March 5, 2007, pp. 101906},
number = 10,
volume = 90,
place = {United States},
year = {Thu Jan 25 00:00:00 EST 2007},
month = {Thu Jan 25 00:00:00 EST 2007}
}
  • The elastic precursor shock strengths of pentaerythritol tetranitrate explosive crystals were measured for [100], [101], [110], and [001] orientations using velocity interferometer system for any reflector instrumentation for samples 3--6 mm thick. Input shock strength was 1.14 GPa. Measured precursor amplitudes were 0.38, 0.58, 0.98, and 1.22 GPa, respectively, for the four orientations. Critical shear stress for the slip system with the maximum resolved shear stress for each shock orientation was computed. Details of the elastic and plastic wave profiles are discussed. Molecular mechanics modeling of the shear induced by the uniaxial strain of a plane shock wave in thismore » molecular crystal was also performed using the AMBER code. This may be the first application of molecular mechanics computation to a shear problem. The modeling correctly predicts the dependence of the precursor amplitude on crystal orientation for the cases considered. The results confirm the importance of steric hindrance to shear in controlling the orientation-dependent strength in molecular crystals and sensitivity to shock initiation of detonation in molecular explosive crystals. Details of the molecular deformations and contributions to the energy barrier to inelastic shear for different orientations are given. The computational results also explain why the [l brace]110[r brace] [l angle]1[bar 1]1[r angle] slip system is observed in quasistatic deformation in spite of having the longest Burgers vector. The dynamics of sterically hindered, shock-induced shear is considered.« less
  • Pentaerythritol tetranitrate single crystals were shocked in four different orientations with the shock direction parallel to the <110>, <001>, <101>, or <100> crystallographic directions. Input stresses were 8.6 or 12.4 GPa. At 12.4 GPa detonation occurred in less than 10-mm run distance of the shock for the <110> and <001> orientations. For the <101> and <100> orientations, denotation was not observed. There is a difference of more than a factor of 2 in run distance to detonation with crystal orientation. The effect can be understood in terms of the available slip systems in the uniaxial strain associated with plane shockmore » compression. In addition, an intermediate velocity transition was observed at 8.6-GPa shock stress for <101> orientation.« less
  • Shock temperatures of pentaerythritol tetranitrate (PETN) single crystals have been measured by using a nanosecond time-resolved spectropyrometric system operated at six discrete wavelengths between 350 and 700 nm. The results show that the shock sensitivity of PETN is strongly dependent on the crystal orientation: Sensitive along the shock propagation normal to the (110) plane, but highly insensitive normal to the (100) plane. The detonation temperature of PETN is, however, independent from the crystal orientation and is determined to be 4140 ({+-}70) K. The time-resolved data yielding the detonation velocity 8.28 ({+-}0.10) mm/{mu}s can be interpreted in the context of amore » modified thermal explosion model. (c) 2000 American Institute of Physics.« less
  • Supercritical shear occurs when the shear stress exceeds the strength of the perfect crystal. An estimate of the theoretical strength of the molecular crystal pentaerythritol tetranitrate is compared to experimental observations of the shock response of this explosive. It is concluded that supercritical shear may be occurring at shock stresses of several GPa in underdriven shocks where there is an elastic wave followed by a slower plastic wave. The induced simultaneous slip on sterically crowded cystallographic planes may be the mechanism for shock initiation of detonation in this explosive, at least in the low stress regime.