Glass Reflections
Cambridge 7th to 9th September



Presenting Author:
Maha Rai
<mr401@kent.ac.uk>

article posted 10 Mar 2015

Maha Rai

Maha Rai is a third year PhD (Physics) research student at the University of Kent, working under the supervision of Dr Gavin Mountjoy.









Molecular dynamics modelling of the structure of
Barium Zirconium Fluoride glasses BaF2-ZrF4
Maha Rai* and Gavin Mountjoy
School of Physical Science, University of Kent, Canterbury, CT2 7NH

BaF2-ZrF4 binary glasses (or ZB glasses) form approximately 70% of multicomponent flurozirconate glasses (ZBLAN glasses) and they are considered the prototype for these glasses of interest for optical technology [1]. These binary glasses also do not follow the general Zachariasen criteria for glass formation because they lack well defined network former structural units, and instead Zr network formers have a mixture of coordination numbers (CN). Molecular dynamics modelling techniques were used to make models of xBaF2-(100-x) ZrF4 glasses with x=25, 33, 40 and 50. The diffraction and the connectivity (Qn) from the model were compared with the experimental results, and with the theoretical calculation based on chemical composition, and showed a good agreement. The typical bond length RZr-F=2.03 and CNZr-F =7.5, and RBa-F=2.82 and CNBa-F=10.4, found in these models were compared to the related crystal structures. Coordination polyhedra of network former (Zr) and modifier (Ba) cations in ZB glasses were also studied by comparing the rotational invariants (Ql) [2] of all known convex regular polyherdra structures.

Figure 1: molecular dynamics model of 33BaF2-67ZrF4 glass (red is fluorine, grey is barium, and orange polyhedral are ZrFCN).


References:

[1] Y. Nomura, M. Nishio, S. Kawato, T. Fuji, IEEE J. Sel. Topics Quantum Electron 21 (2015) 1

[2] D Scott, G. Mountjoy, J. Non-Cryst. Solids 401 (2014) 54-59