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Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface
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10.1063/1.2773720
/content/aip/journal/jcp/127/12/10.1063/1.2773720
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/12/10.1063/1.2773720

Figures

Image of FIG. 1.
FIG. 1.

Temperature dependence of density along isobaric quenches at for a selection of AMLJ- mixtures. From bottom to top: , 0.76, 0.70, 0.64.

Image of FIG. 2.
FIG. 2.

Temperature dependence of density along isobaric quenches at for BMLJ at , , and .

Image of FIG. 3.
FIG. 3.

Effective activation energies for relaxation of large particles, after removal of the high-temperature limit . The dependence of on reduced temperature is shown along isobaric quenches at . Dashed lines are fits to Eq. (3). Upper plot: AMLJ- mixtures for values of size ratio (squares), 0.70 (triangles), and 0.76 (circles). Lower plot: BMLJ (filled circles) and WAHN (open symbols). Inset of upper plot: fragility index of AMLJ- vs . Inset of lower plot: fragility index vs obtained for different isobars in BMLJ.

Image of FIG. 4.
FIG. 4.

Scaled effective activation energies as a function of , along the isobar . Dashed lines are fits to Eq. (3). Upper plot:AMLJ- mixtures, for (squares), (triangles), and (circles). Lower plot: BMLJ (filled circles) and WAHN (open circles).

Image of FIG. 5.
FIG. 5.

Unstable branch of density of states for instantaneous configurations (i-DOS, upper plot) and saddles (s-DOS, lower plot) in BMLJ. Results are shown at four different state points at (from top to bottom, , 1.0, 0.7, 0.6). Dashed lines are fits to Eq. (5).

Image of FIG. 6.
FIG. 6.

Parameter for s-DOS obtained from fits to Eq. (5) as a function of . Upper plot: BMLJ (filled circles) and WAHN (open circles) at . Middle plot: AMLJ-0.64 (filled circles) and AMLJ-0.82 (open circles) at . Lower plot: BMLJ at different pressures, (squares), (circles), and (triangles). Dashed lines are fits of the type, with being roughly system independent.

Image of FIG. 7.
FIG. 7.

Average frequency of stable modes (main plots) and unstable modes (insets) of saddles as a function of . Upper plot: BMLJ (filled circles) and WAHN (open circles) at . Middle plot: AMLJ-0.64 (filled circles) and AMLJ-0.82 (open circles) at . Lower plot: BMLJ at (squares), (circles), and (triangles).

Image of FIG. 8.
FIG. 8.

Upper plot: scatter plot of the fraction of unstable modes against energy of single saddles. Results are shown for WAHN at for three different state points: (squares), (circles), and (triangles). Linear fits of the type (solid lines) are used to estimate the derivative in Eq. (11), i.e., . Lower plot: parametric plot of average unstable modes of saddles against energy of saddles , for WAHN at .

Image of FIG. 9.
FIG. 9.

Effective energy barriers as a function of reduced temperature (left column) and as a function of (right column). Upper plots: WAHN (open circles) and BMLJ (filled circles) at . Lower plots: AMLJ-0.82 (open circles) and AMLJ-0.64 (filled circles) at .

Image of FIG. 10.
FIG. 10.

Effective energy barriers as a function of reduced temperature for BMLJ at (squares), (circles), and (triangles). Dashed lines represent linear fits.

Image of FIG. 11.
FIG. 11.

Participation ratio of average squared displacements on unstable modes as a function of reduced temperature at . Insets show the reduced gyration radius against . Upper plot: AMLJ-0.82 (white squares) and AMLJ-0.64 (black squares). Lower plot: WAHN (white circles) and BMLJ (black circles).

Image of FIG. 12.
FIG. 12.

Distribution of average squared displacements on unstable modes of saddles. Results are shown for small particles (dotted lines), large particles (dashed lines), and irrespective of chemical species (solid lines). Normalization is such that the area under each curve is proportional to the corresponding number concentration. Arrows indicate the average values of for large and small particles. Upper plot: WAHN at , . Lower plot: BMLJ at , .

Image of FIG. 13.
FIG. 13.

Selection of three unstable modes of a quasisaddle sampled in BMLJ at , . The nearly zero mode of the quasisaddle has been ignored. A fourth unstable mode, not shown, is very similar in extension and shape to that shown in (b). For clarity, only particles having square displacements larger than 0.004 are shown, and eigenvectors are scaled logarithmically. Large and small particles are shown as pale large spheres and small darker spheres, respectively. Note the strong localization of mode (a) and the existence of distinct stringlike instabilities of large particles in modes (b) and (c).

Tables

Generic image for table
Table I.

Summary of thermal histories and simulation details. Also shown are the number concentration of large particles , the cutoff scheme used (see the text for definitions), and the value of the cutoff radius . In the case of AMLJ- mixtures, the following values of have been considered: , 0.64, 0.70, 0.73, 0.76, 0.82.

Generic image for table
Table II.

Parameters of fits to Eq. (3) for effective activation energies of large and small species. The reference temperature and the onset temperature are described in the text.

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/content/aip/journal/jcp/127/12/10.1063/1.2773720
2007-09-26
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/12/10.1063/1.2773720
10.1063/1.2773720
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