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Post-shock relaxation in crystalline nitromethane
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10.1063/1.4792438
/content/aip/journal/jcp/138/8/10.1063/1.4792438
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/8/10.1063/1.4792438

Figures

Image of FIG. 1.
FIG. 1.

Definition of molecular layers in the crystal used for analysis of the trajectory results. The flexible slab comprises 310 layers (155 unit cells), each containing 384 molecules. The red line indicates the position of the shock front at the time of analysis (10.0 ps after initiation of the shock) and is defined as layer 0. Layers +1 to +47 are in unshocked material (“ahead of the shock”) while layers −1 to −262 are in the shocked region (“behind the shock”). Layers +1 to +20 comprise the unshocked region used in the analysis discussed in Sec. III B , layers −1 to −10 Region I, layers −61 to −80 Region II, and layers −161 to −180 Region III. The five sets of layer-pairs (−1,−2), (−3,−4), (−5,−6), (−7,−8), and (−9,−10) define, respectively, Subregions Ia, Ib, Ic, Id, and Ie discussed in connection with Fig. 3 . The post-shock distances and times of the layers behind the shock front at the instant of analysis are shown at the bottom of the figure.

Image of FIG. 2.
FIG. 2.

Histograms of the atomic (red) and molecular center-of-mass (blue) kinetic energies for regions at various distances behind the shock front; the temperature values shown were determined by fits (shown by the curves) of the histograms to the Maxwell-Boltzmann distribution, Eq. (1) . The histograms are for regions of material at small, intermediate, and large distances behind the shock front: (a) Region I, (b) Region II, and (c) Region III; see Fig. 1 for definitions of the regions. The greater statistical scatter for Region I compared to Regions II and III results from the fact that there are only 10 molecular layers in Region I compared to 20 in each of the other two regions.

Image of FIG. 3.
FIG. 3.

Histograms of the atomic (red) and molecular center-of-mass (blue) kinetic energies for regions immediately behind the shock front; the temperature values shown were determined by fits (shown by the curves) of the histograms to the Maxwell-Boltzmann distribution, Eq. (1) . The histograms are for five contiguous two-layer-thick regions immediately behind the shock front: Subregions (a) Ia, (b) Ib, (c) Ic, (d) Id, and (e) Ie; see Fig. 1 for definitions of the subregions. The data used to construct this figure are the same as for Fig. 2(a) .

Image of FIG. 4.
FIG. 4.

Atomic (red) and molecular center-of-mass (blue) temperatures (T) obtained from fits of kinetic energy histograms to the Maxwell-Boltzmann distribution, Eq. (1) , for regions at various distances behind the shock front. Red and blue arrows denote regions discussed explicitly in connection with Fig. 2 . The solid curves are fits of the temperatures between and including Regions I and III to Eq. (2) ; blue curve: A = 463.81 K and τ = 1.14 ps; red curve: A = −243.46 K and τ = 1.75 ps. The two curves approach the same asymptote 170 layers behind the shock front; that is, 446 Å or 6.4 ps behind the shock front.

Image of FIG. 5.
FIG. 5.

Distribution of covalent bond distances for the unshocked region (green), Region I (violet), and Region III (orange). (a) C–N bonds, (b) C–H bonds, and (c) N–O bonds. The solid curves are fits of the histogram data to the Gaussian distribution.

Tables

Generic image for table
Table I.

Values of R 0 and FWHM obtained from fits of covalent bond length histograms to the Gaussian distribution and derived effective harmonic force constants.

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/content/aip/journal/jcp/138/8/10.1063/1.4792438
2013-02-28
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Post-shock relaxation in crystalline nitromethane
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/8/10.1063/1.4792438
10.1063/1.4792438
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