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Structure and molecular dynamics of crystalline and liquid anthracene and naphthalene: Possible transient rotator phase of naphthalene
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10.1063/1.3093065
/content/aip/journal/jcp/130/12/10.1063/1.3093065
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/12/10.1063/1.3093065

Figures

Image of FIG. 1.
FIG. 1.

(a) Molecular structure of anthracene and numbering used in the intramolecular part of the present force field. (b) plane of the anthracene crystal viewed down the long molecular axis.

Image of FIG. 2.
FIG. 2.

Pressure (a) and temperature (b) dependencies of the unit cell parameters of anthracene. Open and full symbols are for experimental (Refs. 40, 4, and 3) and numerical data, respectively. ◻, ◼: ; ◇, ◆: ; △, ▲: ; ○, ●: .

Image of FIG. 3.
FIG. 3.

Pressure dependence of the molecular orientation of the anthracene molecule with respect to the crystal cell (see Sec. IV B for definitions). Open and full symbols are for experimental (Ref. 40) and numerical data, respectively. ◻, ◼: ; ◇, ◆: ; ○,●: .

Image of FIG. 4.
FIG. 4.

(a) Superposition of the experimental (Ref. 70) (dark atoms) and simulated (thermally averaged positions, light) unit cells of naphthalene at 184 K viewed projected on the (a) and (b). Isolated “atoms” indicate the corners of the unit cell. (b) Temperature dependence of the unit cell parameters of naphthalene. Same notations as in Fig. 2. Experimental data from Ref. 70.

Image of FIG. 5.
FIG. 5.

Simulated gas phase dimers of anthracene: orthogonal conformation (a), parallel conformation (b); and of naphthalene: oblique T-shapes with parallel (c), perpendicular (d) long axes of the molecules.

Image of FIG. 6.
FIG. 6.

Centers of mass pair correlation function of anthracene at 400, 450, and 475 K, in the crystal (black curves, arrow shows increasing temperature) and at 550 K, in the liquid (in gray). Inset: mass density of the system vs temperature.

Image of FIG. 7.
FIG. 7.

Mean square displacement of anthracene molecules versus time at 400, 450, and 475 K, in the crystal (black curves, arrow shows increasing temperature) and 500, 525, 550, 575, and 600 K in the liquid (in gray). Inset: Arrhenius plot of the diffusion coefficient in the liquid phase.

Image of FIG. 8.
FIG. 8.

Orientational correlation function in the temperature range 400–600 K, in the crystalline phase (black curves) and in the liquid phase (in gray). Inset: integral reorientational lifetimes (●) and (◼) from and , respectively, plotted against the inverse temperature in the liquid phase.

Image of FIG. 9.
FIG. 9.

Melting of anthracene: (a) Diffusion parallel to of the center of mass (black) and of the long axis azimuth (gray) of a single anthracene molecule at the melting transition (at 490 ps) in a simulation at 470 K; (b) distribution of center of mass fluctuations before (black) and after (gray) melting and (c) of long axis azimuth just before (black) and after (gray) melting. Parts (b) and (c) are averaged over all molecules in the simulation, just before and after the transition.

Image of FIG. 10.
FIG. 10.

Melting of naphthalene: (a) Diffusion parallel to of the center of mass (black) and of the long axis azimuth (gray) of a single naphthalene molecule at the melting transition (at 325 ps) in a simulation at 350 K; (b) distribution of center of mass fluctuations before (black) and after (gray) melting and (c) of long axis azimuth just before (black) and after (gray) melting.

Image of FIG. 11.
FIG. 11.

Definition of the angles , , and used to characterize a molecule in the neighborhood of a reference one. is the normal vector to the mean plane of the molecule.

Image of FIG. 12.
FIG. 12.

Histogram of the altazimuthal coordinates (see Fig. 11) of neighboring molecules in liquid anthracene and liquid naphthalene, for center of mass separations 3–4 Å. Contours of the anthracene surface are projected on the plane.

Image of FIG. 13.
FIG. 13.

Illustration of a sandwich dimer conformation from a simulation of liquid anthracene at .

Image of FIG. 14.
FIG. 14.

Histogram of the altazimuthal coordinates (see Fig. 11) of neighboring molecules in liquid anthracene and liquid naphthalene, for center of mass separations 4–5 Å. Contours of the naphthalene surface are projected on the plane.

Image of FIG. 15.
FIG. 15.

Histogram of the altazimuthal coordinates (see Fig. 11) of neighboring molecules in liquid anthracene and liquid naphthalene, for center of mass separations 5–6 Å. Contours of the naphthalene surface are projected on the plane.

Tables

Generic image for table
Table I.

Experimental and simulated thermodynamic data.

Generic image for table
Table II.

Lower vibrational frequencies of anthracene (in ) obtained from the optimized force field (FF) and compared to HF/AM1, B3LYP/6-31G and experimental values.

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/content/aip/journal/jcp/130/12/10.1063/1.3093065
2009-03-23
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Structure and molecular dynamics of crystalline and liquid anthracene and naphthalene: Possible transient rotator phase of naphthalene
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/12/10.1063/1.3093065
10.1063/1.3093065
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