Molecular dynamics calculations of MAX4 melts

Molecular dynamics calculations for MAX4 melts are reported for two different sets of cation/anion radius ratios which were chosen so as to emulate melts such as chloroaluminates and fluoroyttriates. The results are expressed as radial distribution functions, the angular distributions of selected triplets and the number of ions which have particular integer values of the coordination numbers. For the small radius ratio, the A+3 ion is tetrahedrally coordinated and the structure of this completely ionic melt is consistent with the presence of X-, AX-4, A2X-7 and A3X-10 species which equilibrate by the reactions 2AX-4in equilibriumA2X-7+X- and 3AX-4in equilibriumA3X-10+2X-. For the large radius ratio, the A+3 cations are mostly octahedrally coordinated and there is considerable bridging between AX /SUP 3-n/ /SUB n/ moieties which leads to a tendency for long range order