The Amorphous Structure Of The Random Close-packed Model Mc Simulation And Optimization Study

Amorphous metals and alloys have attracted extensive attention for their excellent properties. Studying on the structure of the amorphous metals has become an important aspect in the fields of material and agglomeration physics research. Among the models of amorphous structure, the dense random packing of hard spheres (DRPHS) model is the most basic one. DRPHS model gives a desirable interpretation for the structure of the amorphous metals, and can be simulated by computer using Monte Carlo (MC) method easily. However, because overlaps between the hard spheres are not allowed in DRPHS model, the simulation result of this model can not fit the actual amorphous structure. In order to improve the results of simulation for DRPHS system, people have developed some methods for softening and relaxing the hard spheres. At present, just like the molecular dynamics (MD) simulation method, most of the relaxation methods in MC simulations need an empirical potential functions. The limitation of those MC simulations is that the results are greatly dependent on the potential functions.In this paper, a new method has been developed to optimizing the DRPHS model. In this simulation method, in order to realize the topological arrangement of atoms, the distances between the atoms are restricted by a simple distribution function. Using this method, the atomic configurations satisfying certain atomic locating rules can be simply constructed without choosing or building up potential functions and calculating the force during the simulation. In addition, the method takes the advantages of being applicable to multiple systems. There are four sections in this paper:(1). A computer program has been developed to perform MC simulation for the DRPHS model. Hundreds of configurations of dense random packing structure of hard spheres are generated through two- and three- dimensional simulation. The curves of pair correlation functions (PCF) are calculated and analyzed to discuss the structural details. Additionally, the geometric characteristics of the generated structures in MC simulation for DRPHS model are discussed.(2). To optimize the DRPHS model, firstly the distances between atom neighbors is regarded as random variables which are controlled by uniformity distribution rather than a constant which equal to the diameter of hard sphere. The softened dense packing structure is then generated. The influence of simulation parameters on the obtained results is analyzed. Further more, the amorphous structure is also successfully generated using normal distribution, which is more suitable to the topological placement of atoms.(3). The structure of amorphous metals of Ni, Cu and Al are generated by above optimized dense packing MC method and MD simulation method. The PCF curves are respectively calculated and compared with the MD results. The characteristic parameters in the optimized MC simulation for the amorphous FCC metal structure are obtained that s(disturbing rate) ≈ 0.1 and g(variance) ≈ 0.15.(4). The local structures of the amorphous metals obtained by present simulation work are described and discussed by analyzing the data of PCF and using the pair analysis technology developed by Honeycuttj and Anderrsen. It is concluded from present work that the optimized dense MC method developed in this paper can be used to construct the amorphous structures which are similar to the results of MD simulation. The MC simulation method proposed in this paper can be applied to deeply research on atomic scale structure of amorphous metals as well as MD method.