Construction Of N-body Interatomic Potential For Some Binary Alloy Systems And Its Application

During the past decades, various nonequilibrium materials processingtechniques have been developed and successfully employed to fabricate agreat number of nonequilibrium materials featuring unique properties.Consequently, developing new materials theory to clarify the correlationsamong the microstructure, processing and property of the nonequilibriummaterials has become a strong challenge and an urgent demand. In responding,researchers in the fields of materials and condensed matter physics have paidmuch effort to develop atomic scale theory based on inter-atomic potentialgoverned simulations, and to develop electronic scale theory based onquantum mechanics, namely first-principles and/or ab initio calculations,aiming to formulate new materials theory in a quantitative scheme.Generally, the reliability of the results depends on the interatomicpotential adopted during the molecular dynamics simulation. For binarymetallic alloy system, n-body potential scheme is widely employed, which isusually constructed by fitting the physical properties of various intermetalliccompounds in the alloy system. However, when turned to alloy system thatfeatures positive heat of formation and has no intermetallic compound or thatalthough characterizes negative heat of formation yet exists little information,no enough physical properties necessary in fitting the n-body potential areavailable, and consequently no means to construct a realistic interatomicpotential.Accordingly, based on the forgoing achievements of the author's group,the present thesis proposed a new approach namely first principlescalculations aided construction of n-body potentials. The procedure consiststwo steps, firstly the related physical properties of some possiblenon-equilibrium phases in the alloy system are obtained by first principles;secondly, the obtained physical properties are then employed to fit the n-bodypotential.Following this idea, two reprensitive systems, i.e. Ni-W and Cu-Tasystems, were chosen to fit their respective n-body potential. Firstly, firstprinciples calculations were performed to acquire some physical propertiesand then the Ni-W and Cu-Ta potentials were accordingly constructed underthe Finnis-Sinclair formula and embedded-atom-method, respectively. Thederived potentials were proved to be able to reproduce those importantphysical properties and the reproduced data matched well with those obtainedby first principles calculations or from experiments. Moreover, based on theconstructed potentials, interfacial stability and some other properties of thealloy phases were studied by molecular dynamics simulations and the resultsalso agreed well with the experimental observations, lending support to thefeasibility of the first principles assisted potential construction approach.