Atomic Scale Mechanism of the Transformation of [Formula presented]-Alumina to [Formula presented]-Alumina

Abstract

[Formula presented]-alumina is known to transform to [Formula presented]-alumina and finally to [Formula presented]-alumina upon thermal treatment with a catastrophic loss of porosity and catalytic activity. First-principles calculations were performed to investigate the atomic scale mechanism of the [Formula presented]- to [Formula presented]-alumina transformation. The transformation pathways between the two different forms have been mapped out and identified as a sequence of Al cation migrations. Different possible Al migration paths may be responsible for the experimentally observed formation of domains and twins in [Formula presented]-alumina. The estimated temperature dependence of the conversion rate is in excellent agreement with the experimental transformation temperature. © 2002 The American Physical Society.