A study of the applicability of many-body central force potentials in NiAland TiAl

The applicability and characteristics of the central force many-body potent ials of Finnis-Sinclair-type for NiAl and TiAl are investigated by studying the variation of the energy of these compounds with structural transformat ions that correspond to three distinct paths: tetragonal (B2 --> L1(0)), tr igonal(B2 --> L1(1)) and hexagonal (B2 --> B19). The energy was computed us ing both the central force potentials and the full potential linearized aug mented plane waves (FLAPW) ab initio method. Comparison of these two calcul ations provides a means for the analysis of the efficacy of the potentials. The central force many-body potentials reproduce the results of ab initio calculations very satisfactorily for NiAl. This propounds that they are suf ficient in atomistic modelling of lattice defects in this compound. For TiA l the central force potentials mimic the results of ab initio calculations qualitatively but are unable to differentiate adequately between structures with practically the same separations of the first and second neighbours. However. the present study provides a justification for the use of these po tentials when investigating extended defects in which separations of the fi rst and second nearest neighbours differ significantly from those in the L1 (0) structure.