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Rotational relaxation in simple chain models
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10.1063/1.2798755
/content/aip/journal/jcp/127/21/10.1063/1.2798755
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/21/10.1063/1.2798755

Figures

Image of FIG. 1.
FIG. 1.

Dimensionless diffusion coefficients are plotted in a number of typical manners for the chain center of mass of freely jointed chains. The squares are for repulsive sites and the inverted triangles are for attractive sites. In (A), (B), and (C), the diffusion coefficient is reduced by the site mass , Lennard-Jones well depth , and Lennard-Jones site diameter . In (D), the diffusion coefficient is reduced by , the chain length , the kinetic energy , and the effective hard site diameter ; where is the Boltzmann constant and is the temperature. In (A) the reduced diffusion coefficient is plotted as a function of inverse temperature; in (B), as a function of the volume per site (where is the inverse density); in (C), as a function of the packing fraction ; and, in (D), as a function of reduced packing fraction, where is the location of the ideal glass transition. Error bars are smaller than symbol size. Logarithms are base 10 in all figures.

Image of FIG. 2.
FIG. 2.

is plotted in a number of manners for a high packing fraction case in the FJ system. The solid lines in (A) and (C) are for the single-exponential tail and the solid lines in (B) and (D) are for the Kohlrausch function with . (, , .

Image of FIG. 3.
FIG. 3.

for a low and a high packing fraction repulsive-FR systems is fitted by KWW functions. In addition to the modified LP fit as in Fig. 2(D), a global KWW fit is done. The packing fraction in (A) and (C) is 0.456, while that in (B) and (D) is 0.552. The for the LP fit is constant while the global decreased.

Image of FIG. 4.
FIG. 4.

The rotational relaxation times from as a function of translational relaxation time for the chain center of mass. In (A). and are plotted against for FJ chains. In (B), this is repeated for FR chains. In (C), the ratio of to is plotted as a function of for both FJ and FR chains. In (D), the ratio of to is plotted as a function of for both FJ and FR chains. In (A) and (B) circles are for repulsive ; the squares, for repulsive ; the inverted triangles, for attractive ; and the triangles, for attractive . In (C) and (D) circles are for attractive FJ; the squares, for repulsive FJ; the triangles, for attractive FR; and the inverted triangles, for repulsive FR. Lines have slopes of 1 and are for reference.

Image of FIG. 5.
FIG. 5.

Modified Lindsey-Patterson of representative systems for both FJ and FR cases. This entails plotting against . When plotted as such, the KWW function is linear with a slope of . In (A), is analyzed for attractive FJ and, in (B), for attractive-FR systems. Results have been shifted both horizontally and vertically for clarity. In (C), has been analyzed for both FJ and FR systems. In (D), has been analyzed for both FJ and FR systems. In both (C) and (D), the times have been reduced by the translational relaxation times for the chain center of mass, and the FR results have all been shifted down in the vertical direction by 1 for clarity. Unlike in (A) and (B), there are no other shifts of the data. The FJ packing fractions in (A) are, from upper curve to lower, 0.429, 0.537, 0.566, 0.6178, and 0.630. The FR packing fractions in (B) are, from upper curve to lower, 0.494, 0.504, 0.517, 0.538, and 0.552. These packing fraction are also used in (C) and (D). In (A), all lines have slopes of 0.75 except the uppermost, which has a slope of 0.68. In (B), all lines have slopes of 0.68 except the lowestmost, which has a slope of 0.75.

Image of FIG. 6.
FIG. 6.

(A) and (B) are linear-log plots of the data in Fig. 5. (A) is for FJ systems, and (B) for FR systems. In order to show the degree of collapse, only curves through the data points are shown. In (C) are the translational relaxation times used to reduce the time scales in (A) and (B) as well as in Fig. 5. In (D) are the ratios of relaxation time for E to that of B for both FJ and FR systems. The circles are for attractive FJ; the squares, for repulsive FJ; the inverted triangles, for attractive FR; and the triangles, for repulsive FR.

Tables

Generic image for table
Table I.

State points simulated. Temperature in units of . Density in units of . Pressure in units of .

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/content/aip/journal/jcp/127/21/10.1063/1.2798755
2007-12-05
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Rotational relaxation in simple chain models
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/21/10.1063/1.2798755
10.1063/1.2798755
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