  The addition of transition metal elements can significantly modify physical
properties of intermetalic compounds. We studied the influence of Molybdenum
and Vanadium additives on thermal expansion coefficient (CTE) of Fe/sub 3/Al
and FeAl over the wide range of temperatures. The site preference of both
transition metals was determined by full-potential LMTO method within the
grandcanonical formalism. At low temperatures CTEs were found directly from the
FP-LMTO calculations by incorporating them into the Debye model of a solid. The
obtained thermal expansion for pure Fe/sub 3/Al and FeAl is within 10% of its
experimentally measured values. At high temperatures we performed molecular
dynamics simulations based on our many-body atomistic potentials. The
parameters were fitted to reproduce the total energy of a crystal under various
types of deformations obtained by FP-LMTO method and were tested with respect
to different structures and vacancy formation energies. Our calculations show
that addition of V decreases the CTEs of both iron-aluminides, while the
addition of Mo makes Fe/sub 3/Al DO3 structure unstable.
