LOCAL-STRUCTURE OF ALKALINE-EARTH BOROALUMINATE CRYSTALS AND GLASSES .1., CRYSTAL CHEMICAL CONCEPTS STRUCTURAL PREDICTIONS AND COMPARISONS TO KNOWN CRYSTAL-STRUCTURES

This paper presents a model which predicts glass structures based on local charge balance considerations. The model is shown to be consistent with known structures of borate, aluminate, and boroaluminate crystals and predicts that boroaluminate glasses should contain 3- and 4-coordinate boron, 4-, 5-, and 6-coordinate aluminum, and oxygens coordinated to one, two, three, and perhaps even four network-forming cations. The predicted glass structures are more complex than previous models for boroaluminate glasses, explaining the solid-state NMR data for the boroaluminate glasses discussed in Part II.