Parameters of the Fluctuation Free Volume Theory for Glasses in the Ge–As–Se System

• Published in: Glass physics and chemistry Vol. 30; no. 5; pp. 406 - 414
• Main Authors: Mel'nichenko, T. D., Rizak, V. M., Mel'nichenko, T. N., Fedelesh, V. I.
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01-09-2004
• Subjects: Fluctuation; Frozen; Glass; Glass transition; Hogs; Mathematical analysis; Poissons ratio; Ultrasound; Volume fraction
• ISSN: 1087-6596; 1608-313X
• DOI: 10.1023/B:GPAC.0000045920.01447.ba

The fraction of fluctuation free volume (f^sub g^ = V^sub f^/V) frozen at the glass transition temperature T^sub g^ is determined from the temperature dependence of the viscosity in the glass transition range in terms of the Vogel-Fulcher-Tammann equation and the formula α^sub f^ T^sub g^ ΔαT^sub g^ = f^sub g^ln(1/f^sub g^). The fluctuation free volume fractions f^sub g^ obtained according to these two procedures for glasses in the Ge-As-Se system are in quite reasonable agreement. The energies E^sub h^ of formation of fluctuation microvoids and their volumes V^sub h^ are calculated. It is demonstrated that the quantities f^sub g^, E^sub h^, and V^sub h^ and the ratio of the microhardness H to T^sub g^ depend substantially on the glass structure and can serve as characteristics of the rigidity of the glass networks. It is noted that the fluctuation free volume fraction f^sub g^ is a nonmonotonic function of the mean coordination number Z^sub m^ and that it exhibits a specific dependence on the lattice Grüneisen parameter γ. The Poisson ratios μ are estimated from the fluctuation free volume fraction f^sub g^ with the use of the relationship f^sub g^ln(1/f^sub g^) = (ProQuest: Formulae and/or non-USASCII text omitted; see image)>. It is shown that the Poisson ratios μ thus obtained are close to those calculated from the data on the transverse (V^sub s^) and longitudinal (V^sub l^) velocities of ultrasound.[PUBLICATION ABSTRACT]