Interatomic Manybody Potentials Of Ni-Al Alloys Derived By Lattice Inversion Method

Ni-Al alloys are the candidates for high-temperature structural materials because of specific strength, high specific stiffness, excellent oxidation resistance and yield strength anomaly at high temperature. Nowadays they can be widely used in military and civilian fields, and then attracting special attention from many researchers since the1860s. Although the great progress has been made in the experiments and applications of Ni-Al alloys, there still require some efforts to improve the properties of binary alloys, such as the brittleness at room temperature, poor toughness and limited high temperature strength. From the viewpoint of atomistic scale, the brittleness problem comes mainly from special alloy lattice structure and defects configuration. This indicates that the detail of atomic configurations play an important role to understand the mechanism of limited performance of the alloys. So based on interatomic potentials, a large-scale atomistic simulation provides an effective method for us to interpret the relationship between the atomic level structure and properties.The effectiveness of large-scale atomistic simulations is basically decided by the validity of interatomic potentials. In most of the previous work, the inter-atomic potentials were started form prior selection of function forms with some adjustable parameters, and then the potential parameters were obtained by fitting to the experimental data or calculations. This led to some uncertainty and arbitrariness which were inevitably involved by providing several sets of potential parameters.In the present work, in terms of the stable structures, several virtual structures were introduced to determine the contributions from short-ranged pairwise potentials and long-ranged embedded atoms. By the multiple-lattice inversion technique, we firstly obtained the pairwise potential curves, atomic electron density and density function to describe the inter-action between the like-atoms in Ni-Al alloys, and the calculations of their static mechanical properties and the phonon spectrum confirme the validity of this set of potentials. Subsequently the B3and B10structures were used, the equilibrium atomic electron density ratio peAl/peNi was determined to take account the cross-interactions between the unlike-atoms in Ni-Al alloys.In order to test the validity of the present interatomic potentials, some molecular-mechanical simulations were performed to check whether the structural parameters and the related properties have been well described. The calculations show that the present interatomic potentials not only well reproduce the static structural properties taken as the potentials data source from first-principle calculations, but also well give the lattice parmeters, elastic modulus,point defect and phonon spectrum of Ni-Al alloys which were not included in the potential database and most of the calculated results are in good agreement with previous other calculations. Then the inverted EAM potentials were used to reasonably describe the Bain and trigonal transformation pathes from the B2to Ll0and Ll1phases of Ni-Al under uniaxial stress, respectively. In summary, the new virtual structures with lattice inversion method are successfully used to obtain EAM interatomic potentials for Ni-Al alloys which are suitable for modelling of binary alloys properties over a wide range of interatomic distances and coordination environments of the atoms, so the derived potentials are confirmed to valid covering the most of phase space of Ni-Al alloys. This indicates that the present method and corresponding results exhibit a promising way for the further atomistic simualtions of binary alloys, especially the virtual-structures method is an available strategy to determine expain the cross-interaction between the different metal atoms..