article posted 14 April 2016
Dr Gavin Mountjoy is Reader in Condensed Matter Physics at the University of Kent. He first studied Physics at Victoria
University of Wellington where he obtained a BSc. A Commonwealth Scholarship enabled him to undertake a PhD in the Microstructural Physics Group at the Cavendish
Laboratory, University of Cambridge. This was followed by work as a Research Associate in the Center for Solid State Science at Arizona State University, U.S.A. In
2001 Gavin was appointed as a Lecturer in the School of Physical Sciences at University of Kent. In 2006 undertook a Marie Curie Intra-European Fellowship in the
Functional Materials Group, University of Cagliari, Italy. Following this Gavin returned to University of Kent as a Senior Lecture and subsequently held role of Head
of Functional Materials Group.
Homogeneous and inhomogeneous modifier cation distributions
in oxide glasses from molecular dynamics
G. Mountjoy*, M. Rai, and L. Swansbury
School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
The distribution of modifier cations in oxide glasses may be described qualitatively, e.g. as “channels”, or quantitatively, e.g. using distribution functions.
Recent results from classical molecular dynamics modelling illustrate details of homogeneous and inhomogeneous modifier cation distributions in oxide glasses.
This includes key scenarios which are typical in silicate glasses. At very low concentrations modifier cations are dopants and are predicted to follow a fundamental
dopant distribution. At moderate concentrations modifier cations can be phase separated, whereas at higher concentrations they tend not to be. Phase separation can
be distinguished by quantitative evaluation of the fluctuations in local number density, and examples will be given for Mg, Ca and Ba silicate glasses (see Figure 1).
In non-phase separated glasses where two different modifier cations are present there is still the question about whether there is homogeneous mixing. Results for
silicate and xNaO-(50-x)CaO-50P2
phosphate glasses show that this is a very good approximation, and any deviations from this are subtle.
Figure 1: the local number density of Ba in 62 Ĺ wide model of 25BaO-75SiO2