Atomic and Electronic Structure in MgO-SiO 2 .

Understanding disordered structure is difficult due to insufficient information in experimental data. Here, we overcome this issue by using a combination of diffraction and simulation to investigate oxygen packing and network topology in glassy ( g -) and liquid ( l -) MgO-SiO 2 based on a comparison with the crystalline topology. We find that packing of oxygen atoms in Mg 2 SiO 4 is larger than that in MgSiO 3 , and that of the glasses is larger than that of the liquids. Moreover, topological analysis suggests that topological similarity between crystalline ( c )- and g -( l -) Mg 2 SiO 4 is the signature of low glass-forming ability (GFA), and high GFA g -( l- ) MgSiO 3 shows a unique glass topology, which is different from c- MgSiO 3 . We also find that the lowest unoccupied molecular orbital (LUMO) is a free electron-like state at a void site of magnesium atom arising from decreased oxygen coordination, which is far away from crystalline oxides in which LUMO is occupied by oxygen's 3 s orbital state in g - and l -MgO-SiO 2 , suggesting that electronic structure does not play an important role to determine GFA. We finally concluded the GFA of MgO-SiO 2 binary is dominated by the atomic structure in terms of network topology.