AbstractRecent developments in the use of quantum mechanics to make structural predictions and provide insights at the atomic level are reviewed with respect to intermetallics. In particular, the question is addressed of why some tetragonal D022trialuminides (e.g. TiAl3) can be stabilised with the cubic L12structure by alloying additions but others (e.g. NbAl3) cannot, and why, if the cubic phase is stabilised, it remains brittle.MST/1543