Molecular Dynamics Simulation Of Microstructure Of Metallic Glass

As a new developed material,metallic glass has always been one of the most important research fields in condensed matter physics and material physics.The understanding of the atomic arrangement sequence of metallic glass can help us understand the glass formation process deeply.At present,although we can obtain relatively reliable atomic spatial positions of metallic glasses with the help of computer simulation,it is still a mystery to accurately characterize the atomic structure order of metallic glass system because of the disordered long-range arrangement of atoms in metallic glass system.In this paper,we focus on the following subjects.Firstly,we developed a new structure analysis method named‘sharing coordination atoms'(SCA)method,which is used to effectively characterize the local structural development of metallic glass from short range to medium range of metallic glass;Secondly,we study the structural heterogeneity in Cu₆₄Zr₃₆ metallic glass.The main contents are as following.1.The history,formation mechanism and research techniques of metallic glass are briefly summarized.Some common structural analysis methods used in simulation,such as radial distribution function,bond-angle distribution function,HA index method,Voronoi index method and atomic cluster alignment method are introduced.2.Using molecular dynamics simulation method,based on HA index and SCA index,the growth mode of Cu₆₄Zr₃₆ and Ni₆₄Zr₃₆ metallic glasses from short range order to medium range order was studied.The results show that,in the Cu₆₄Zr₃₆ metallic glass,the atoms grow mainly in Bergman mode in medium range order.Unlike Cu₆₄Zr₃₆metallic glass,the Bergman arrangement in medium range scale of Ni₆₄Zr₃₆ alloy is not obvious.It shows that SCA method can effectively be used to analyze the medium range order structure of metallic glass,which is helpful to improve the understanding of the structure of metallic glass.3.Using molecular dynamics simulation method,the heterogeneity of Cu Zr alloys system was studied.We find that there is not only structural heterogeneity but also potential energy heterogeneity in metallic glass.The structural heterogeneity is mainly caused by the heterogeneity of fivefold symmetry.The structure with higher fivefold symmetry usually has relatively lower energy,which indicates that these two heterogeneities maybe intrinsically related.However,they are not completely overlapped in space when we examined the constituted atoms of these two heterogeneities.