A molecular dynamics simulation interpretation of neutron and x-ray diffraction measurements on singlephase Y2O3–Al2O3 glasses

Abstract

Molecular dynamics simulations and complementary neutron and x-ray diffractionstudies have been carried out within the single phase glass forming range of(Y2O3)x(Al2O3)(100−x), forx = 27 and 30.For x = 27, the experimental Al–O and Y–O coordination numbers are found to be4.9 ± 0.2 and6.9 ± 0.4 respectively, compared to 4.4 and 6.8 obtained from the simulation. Similar results were found forx = 30.An R-factor analysis showed that the simulation models agreed to within∼6% of the diffraction data in both cases. The Al–O polyhedra are dominated by fourfoldand fivefold species and the Y–O local coordinations are dominated by sixfold,sevenfold and eightfold polyhedra. Analysis of the oxygen environments reveals alarge number of combinations, which explains the high entropy of single phaseyttrium aluminate glasses and melts. Of these, the largest variation betweenx = 27 and 30 is found in the number of aluminum oxygen triclusters (oxygens bonded to three Al) andoxygens surrounded by three Y and a single Al. The most abundant connections are between theAlOx andYOy polyhedra of which 30% are edge shared. The majority ofAlOx–AlOx connections were found to be corner shared.