[UCI-Calit2] Upcoming lecture: The dispersion of the structural relaxation: a governing factor of the structural relaxation time and glass transition

[Anna Lynn SPITZER]

Title:                            The dispersion of the structural
relaxation: a governing factor of the structural relaxation time and
glass transition

 

Speaker:                      Kia.L.Ngai

 

Time:                           2 p.m.

 

Date:                           Friday, May 13, 2005

 

Location:                     Natural Sciences I, Room 1114

 

Abstract:                      Glass transition by decreasing
temperature or increasing pressure occurs when the structural relaxation
time, ta, becomes so long that the system falls out of equilibrium.
Theories and models including the celebrated free volume and
configurational entropy models explain the glass transition by invoking
one quantity or the other that governs the structural relaxation time.
However, invariably the dispersion of the structural relaxation is
derived either as a parallel consequence independent ofta, or considered
as an afterthought.  In no way the dispersion plays any fundamental role
in determining ta and other dynamic properties. In this paper, we show
these theories and models are untenable because they cannot explain a
general experimental fact recently discovered in many glass-formers. The
remarkable experimental finding from dielectric relaxation data
collected at various combinations of temperature and pressure but having
the same ta is that they also have exactly the same dispersion. If the
dispersion of the structural relaxation is another consequence of a
theory or model independent ofta, it is unlikely that both ta and the
dispersion can be maintained invariant to the same combinations of
temperature and pressure.

On the other hand, the Coupling Model of the speaker can explain the
observed properties. Other recent advances of the Coupling Model will be
presented. 

 

Bio:                              Kia Ngai is a senior scientist and
theoretical consultant at the Electronic Science & Technology Division,
Naval Research Laboratory, in Washington,                           D.C.
He received his doctorate in physics from the University of Chicago and
has received the 1997 Navy Superior Civilian Service Award and the 

                                    1986 Sigma Xi Pure Science Award.
Ngai has organized several conferences on relaxations in complex
systems, including the first one in 1984, and
several subsequent international discussion meetings from 1990-2005.

 

Hosts:                          The Institute for Surface and Interface
Science (ISIS), and professors Doug Mills and Albert Yee

 

 

This seminar is free and open to the public

 

 

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