Trends in the structural stability of aluminum-rich transition-metal aluminides

We present a theory on the structural stability of aluminum-rich transition-metal (TM) compounds. Our approach incorporates electronic-structure-based potential-energy functions for the aluminides. It is shown that an argument based on the short-range Al-TM interactions can explain the transition from close-packed structures for early TM aluminides to open and complex structures for middle and late TM aluminides. On the other hand, the medium- and long-range interactions between the TM atoms are responsible for the particular choice of a close-packed (or complex) structure for a given aluminide.