Glass structure, rigidity transitions and the intermediate phase in the ternary

Y. Wang; P. Boolchand; M. Micoulaut

doi:10.1209/epl/i2000-00485-9

All issues

Volume 52 / No 6 (December II 2000)

Europhys. Lett., 52 6 (2000) 633-639

Abstract

Issue		Europhys. Lett. Volume 52, Number 6, December II 2000


Page(s)		633 - 639
Section		Condensed matter: structure, mechanical and thermal properties
DOI		https://doi.org/10.1209/epl/i2000-00485-9
Published online		01 September 2002

Europhys. Lett., 52 (6), pp. 633-639 (2000)

Glass structure, rigidity transitions and the intermediate phase in the $\ab{Ge\mbox{-}As\mbox{-}Se}$ ternary

Y. Wang¹, P. Boolchand¹ and M. Micoulaut²

¹ Department of Electrical & Computer Engineering and Computer Science University of Cincinnati - Cincinnati, OH 45221-0030, USA
² Laboratoire de Physique Theorique des Liquides, Université Pierre et Marie Curie Tour 16, 4 Place Jussieu, 75252 Paris, Cedex 05, France

Received: 15 May 2000
Accepted: 16 October 2000

Abstract

The non-reversing heat flow, $\Delta H_{\ab{nr}}(x)$ near $T_{\ab g}$ in ternary $\ab{Ge}_x\ab{As}_x\ab{Se}_{1-2x}$ glasses is examined by temperature-modulated differential scanning calorimetry. The $\Delta H_{\ab{nr}}(x)$ term shows a deep minimum (which is almost zero) in the 0.09 < x < 0.14 range, identified with the intermediate phase, and an increase, both at low x (< 0.09) in the floppy phase and at high x (> 0.14) in the stressed rigid phase. Expressed in terms of mean coordination number, $\bar r = 2+3x$ , the large width, $\Delta\bar r= r_{\ab c}(1)-r_{\ab c}(2) = 0.15$ , of the intermediate phase and its low onset value $r_{\ab c}(1) = 2.27$ are shown to be consistent with the presence of $\ab{Se=As(Se_{1/2})_3}$ units in addition to pyramidal $\ab{As(Se_{1/2})_3}$ and tetrahedral $\ab{Ge(Se_{1/2})_4}$ units in the stress-free backbone. The vanishing of $\Delta H_{\ab{nr}}(x)$ in the intermediate phase is in harmony with the notion that the number of Lagrangian constraints/atom exhausts the three available degrees of freedom, and leaves the backbone in a mechanically stress-free state.

PACS: 61.43.Fs – Glasses / 63.50.+x – Vibrational states in disordered systems / 61.20.-p – Structure of liquids

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