-
12
-
-
0038930453
-
-
developed a method to determine the equilibrium heat capacity of glycerol to [formula omitted] 8 °C below the normal glass transition temperature.
-
(1937)
J. Am. Chem. Soc.
, vol.59
, pp. 2495
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-
Oblad, A.G.1
Newton, R.F.2
-
23
-
-
85038187836
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18,19
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-
-
-
27
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-
84950578517
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We should note that our cooperative bond chain is formally equivalent to an Ising chain in an external magnetic field. (This was first pointed out to us by M. Goldstein.) An external field biases the energy of the alternative spin directions.
-
In practice the two cases will be distinguished by the circumstance that in the bond lattice the bond-breaking (noncooperative) term is always larger than the bond-weakening (cooperative) term.
-
-
-
-
28
-
-
85038174493
-
This model for the configurational heat capacity is the equivalent in terms of oversimplification of the Einstein single oscillator model for the vibrational heat capacity.
-
-
-
-
31
-
-
85038182327
-
have previously been quoted for a “two structural state” model of the glass transition by Leidecker et al. (see Ref. 9)
-
-
-
-
32
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-
84950595405
-
related expressions have also been derived for a linear model by
-
National Science Foundation Report Grant No. GP 5979
-
-
-
Goldstein, M.1
-
36
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-
85038190793
-
Higher excited state will lead to adjacent “off” elements and a new term in the excitation energy [formula omitted] of similar magnitude to [formula omitted]
-
-
-
-
43
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-
85038172006
-
33 (except for use of a constant total configurational energy constraint in place of a total free volume constraint) may yield Eq. (11) with ξ identified as [formula omitted] here M is the number of large regions into which the [formula omitted] element bond lattice is divided, [formula omitted] is the critical configurational energy per region necessary for a rearrangement to occur, and γ is an overlap correction factor [formula omitted] which allows for the fact that any arbitrary division of the lattice into regions will fail to count critical fluctuations which overlap adjacent regions.
-
Since [formula omitted] is [formula omitted] the condition for [formula omitted] in Eq. (11) (as seems to apply in practice) is that [formula omitted] which would imply that the critical condition for irreversible motion is that a fraction γ of the possible bonds in the region are broken. Unfortunately, it is doubtful that, for such high degrees of disruption, the modified Cohen-Turnbull argument suggested here can be justified.
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-
-
-
56
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-
85038175318
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4
-
Anyone of the potential energy minima of Goldstein’s model has its equivalent in the present model in a particular distribution of a particular number of excitations (“broken bonds”) across the bond lattice. The abnormal fluctuation in local concentration of broken bonds considered necessary for a rearrangement to occur in the present model constitutes a free energy barrier to motion, but one which is closely correlated with the configurational thermodynamic state of the liquid.
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-
-
-
58
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-
0001515576
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points to the essential identity of heat capacities of quenched and annealed o-terphenyl glass at temperatures between [formula omitted] and 2 °K
-
as evidence that the entropy frozen in at [formula omitted] cannot have a large vibrational component.
-
(1972)
J. Chem. Phys.
, vol.56
, pp. 503
-
-
Chang, S.S.1
Besful, A.B.2
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59
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-
85038182921
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Current studies [J. H. R. Clarke (private communication)]
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-
-
-
60
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-
85038184046
-
of a buildup in Boltzmann factor-corrected Rayleigh wing intensity in many glasses as T increases above [formula omitted] seem particularly promising. These studies may be expected to provide some evidence for or against the changes in density of vibrational states on excitation implied by nonzero values of [formula omitted] in Eq. (2) (in the harmonic oscillator case [formula omitted] per mole of oscillators changing frequency from [formula omitted] to [formula omitted] It may be significant that, in the case of [formula omitted] where [formula omitted] is only 1 e.u. (Fig. 2), little or no buildup in Raman intensity is detected. We note that changes in lattice frequencies with state of order are also invoked to account for measured heat capacities in lambda-type order-disorder transitions
-
(private communication) Buildups in low frequency Raman intensity are also observed through such transitions.
-
(1960)
J. Chem. Phys.
, vol.33
, pp. 1299
-
-
Matthew, J.A.D.1
Wojtowicz, P.J.2
Kirkwood, J.G.3
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