Rings in Network Glasses The B2O3 Case

Universite Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris, France e-mail ferlat impmc.upmc.fr 

Atomistic simulations are therefore essential tools since they provide 3D atomic structures fl om which about any n-body correlation function can be computed. Beyond the traditional two-body correlation functions, g2(r), it is also quite common to visualise angular correlations. 

In oxide systems, one usually defines the nth order of a ring by the number of network-former cations (Si for silica, B for boron oxide) involved in the closed loop. Since each polyhedra (Si04 tetrahedra in siUca, BO3 triangles in boron oxide) is corner-shared by an oxygen, a n-fold ring contains 2n cation-oxygen bonds. 

Unfortunately, there is no experimental technique that can probe the entire rings distribution in glasses. Direct imaging of the rings has been recently achieved thanks 

Since we are mostly interested in the smaller rings, we sweep under the carpet that several possible definitions of rings exist which can affect the results for the larger rings distribution [23-26]. A discussion of these definitions and of the associated technical issues can be found in [25]. 

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