Anharmonic Oscillations and Tg, Tm Transitions

[img]PDF - Authorized users only
Language: English
87Kb
Title:Anharmonic Oscillations and Tg, Tm Transitions
Creators:
Hlaváček, Bořivoj
Khünová, Viera
Večeřa, Miroslav
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 61, 1, pp. 44-58
Uncontrolled Keywords:Jump frequency at glass transition, Anharmonic oscillations, Melting point, Glass transition

Abstract

A working hypothesis has been developed to account for a change in character of thermal motion at glass transition. According to this hypothesis the pronounced onset of anharmonic vibrations is responsible for a stepwise increase in the thermal expansion coefficient alpha as well as in the similar temperature change in specific heat coefficient <i>c</i><sub>p</sub>. In this paper the both transitions (the first order transition at melting point and the second order transition at <i>T</i><sub>g</sub>) are investigated on the basis of the viewpoint connected with the change in characteristics of motion of the particles, so typical for an onset of a liquid state. At present, two different definitions for the coefficient of thermal expansion are used. One is usually adopted in polymer physics, where also the statistical approach to polymer chains configurations plays the major role in <i>T</i><sub>g</sub> definition. However, the statistical configurational approach of polymer physics cannot be applied directly to the inorganic glasses and also does not provide any explanation of relatively small changes in <i>c</i><sub>p</sub> values at melting point transition which sometime occur. Using the interpretation of solid state physics, the present paper intends to make a first step and bridge over the gap between these two approaches and to explain the <i>T</i><sub>g</sub> transition in dynamic terms, common to the polymers as well as to the low molecular weight substances.

Title:Anharmonic Oscillations and Tg, Tm Transitions
Creators:
Hlaváček, Bořivoj
Khünová, Viera
Večeřa, Miroslav
Uncontrolled Keywords:Jump frequency at glass transition, Anharmonic oscillations, Melting point, Glass transition
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:61
Number:1
Page Range:pp. 44-58
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19960044UNSPECIFIED
ID Code:912
Item Type:Article
Deposited On:06 Feb 2009 17:05
Last Modified:06 Feb 2009 16:05

Citation

Hlaváček, Bořivoj; Khünová, Viera; Večeřa, Miroslav (1996) Anharmonic Oscillations and Tg, Tm Transitions. Collection of Czechoslovak Chemical Communications, 61 (1). pp. 44-58. ISSN 0010-0765

Repository Staff Only: item control page