Complex Crystal and Glass Structures

Abstract

In most simple metal–oxide structures, rC << rA and the structures can be built up by considering a nearly close-packed arrangement of oxygen ions with cations located in interstices. The ionic radius ratios given earlier are useful and provide a means of predicting the coordination number (CN) of a particular compound, and often the predictions are in good agreement with observed values. In cases where the observed CN differs greatly from the expected value, such as 12 for K+ in mica, KAl3Si3O10(OH)2, it is probable that the other ions present play the most important part in determining the arrangement.