Atomic and Electronic Structure in MgO-SiO₂.

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• Disordered structures in materials like glassy and liquid MgO-SiO2 are challenging to analyze due to limited experimental data.
• Understanding the relationship between atomic structure and glass-forming ability (GFA) is crucial for designing new materials.

Purpose of the Study:

• To investigate oxygen packing and network topology in glassy (g-) and liquid (l-) MgO-SiO2.
• To compare the atomic structures of crystalline, glassy, and liquid states to understand GFA.
• To determine the role of electronic structure in the GFA of MgO-SiO2 systems.

Main Methods:

• Combined experimental diffraction and computational simulation techniques.
• Topological analysis of atomic structures.
• Calculation of the lowest unoccupied molecular orbital (LUMO) electronic states.

Main Results:

• Oxygen packing is larger in Mg2SiO4 than MgSiO3, and larger in glasses than liquids.
• Topological similarity between crystalline and glassy/liquid Mg2SiO4 correlates with low GFA.
• High GFA MgSiO3 exhibits a distinct glass topology compared to its crystalline form.
• LUMO states in MgO-SiO2 glasses are localized at void sites, unlike crystalline oxides, suggesting electronic structure is not a primary GFA determinant.

Conclusions:

• The GFA of MgO-SiO2 binary systems is primarily governed by atomic structure, specifically network topology.
• Topological analysis provides key insights into the GFA of oxide glasses.
• Electronic structure, particularly LUMO localization, does not appear to be a dominant factor controlling GFA in these systems.