A microstructure of martensite which is not a minimiser of energy: The \(X\)-interface (Q1337978)

We investigate the \(X\)-interface, a microstructure observed in indium- thallium; it was known how simple martensitic microstructures can be represented by sequences of elastic deformations which minimise a free- energy functional. In contrast, we show that the \(X\)-interface cannot be represented by such a sequence. In an attempt to understand this result we develop a less restrictive theory based on Ericksen's ideas about low- energy modes of deformation for martensitic materials. Our calculations apply only to cubic-to-tetragonal transformations.