Topological versus chemical ordering in network glasses at intermediate and extended length scales

被引:230
作者
Salmon, PS [1 ]
Martin, RA
Mason, PE
Cuello, GJ
机构
[1] Univ Bath, Dept Phys, Bath BA2 7AY, Avon, England
[2] Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England
[3] Inst Max Von Laue Paul Langevin, F-38042 Grenoble, France
基金
英国工程与自然科学研究理事会;
关键词
D O I
10.1038/nature03475
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Atomic ordering in network glasses on length scales longer than nearest-neighbour length scales has long been a source of controversy(1-6). Detailed experimental information is therefore necessary to understand both the network properties and the fundamentals of glass formation. Here we address the problem by investigating topological and chemical ordering in structurally disordered AX(2) systems by applying the method of isotopic substitution in neutron diffraction to glassy ZnCl2. This system may be regarded as a prototypical ionic network forming glass, provided that ion polarization effects are taken into account(7), and has thus been the focus of much attention(8-14). By experiment, we show that both the topological and chemical ordering are described by two length scales at distances greater than nearest-neighbour length scales. One of these is associated with the intermediate range, as manifested by the appearance in the measured diffraction patterns of a first sharp diffraction peak at 1.09( 3) angstrom(-1); the other is associated with an extended range, which shows ordering in the glass out to 62( 4) angstrom. We also find that these general features are characteristic of glassy GeSe2, a prototypical covalently bonded network material(15,16). The results therefore offer structural insight into those length scales that determine many important aspects of supercooled liquid and glass phenomenology(11).
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页码:75 / 78
页数:4
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