The issue, composition dependence of glass-forming ability (GFA) in metallic glasses (MG), has been investigated by systematic experimental measurements coupled with theoretical calculations in Cu-Zr and Ni-Nb alloy systems. It is found that the atomic-level packing efficiency strongly relates to their GFA. The best GFA is located at the largest difference in the packing efficiency of the solute-centered clusters between the glassy and crystal alloys in both MG systems. This work provides an understanding of GFA from atomic level and will shed light on the development of new MGs with larger critical sizes.

https://link.aps.org/accepted/10.1103/PhysRevLett.109.105502

Atomic-scale mechanisms of the glass-forming ability in metallic glasses.

We have studied the structure and dynamics of a series of Zr1−xCux metallic liquids at temperatures of 1500 and 1300 K. We found that as the Cu composition increases, the Zr–Zr order undergoes considerable transition, which can be attributed to the different size of Zr and Cu atoms. The diffusivities of both Cu and Zr atoms become lower at the composition range corresponding to good glass forming region, i.e., 0.50≤x≤0.70. We found that the lower diffusivities for the intermediate composition range are correlated with the concentration of some specific clusters, including icosahedra, which can be screened out automatically and unbiasedly by using direct atomic dynamics analysis. Our analysis for the dynamic properties of high temperature liquids of ZrCu metallic alloys shows that the icosahedral clusters together with some other pentagon-rich Voronoi clusters are responsible for slowing dynamics. Cluster lifetime analysis indicates that the slow clusters mobility could be originated in their energy.

Microscopic origin of slow dynamics at the good glass forming composition range in Zr1-xCux metallic liquids

Correlation between the cluster energy and its population and dynamics can provide a better understanding of the complicated energy landscape of disordered metallic systems. We propose a method to analyze the cluster energy distribution for different kinds of short-range order (local clusters) in liquid and glass systems. By applying this analysis to an interesting and important glass forming system— Cu 64.5 Zr 35.5 we observe a direct correlation between the energy and dynamics of the cluster in this realistic glass-forming system. This study suggests that dynamic arrest originates from the environment-dependent energetics of local clusters.

Energetics of local clusters in Cu64.5Zr35.5 metallic liquid and glass

Anomalous structural dynamics in liquid Al80Cu20: An ab initio molecular dynamics study

Temperature-dependent structure evolution in liquid gallium

Solidification of crystalline phases from the liquid is a highly complex, yet critically important process involving phase selection and growth that is of academic interest and also has many practical considerations. 1 In order to fully model this process at the atomic level, we must begin with an accurate description of the local atomic structure of the liquid and further describe how it changes as a function of temperature. Accurately describing the liquid state is complicated by its lack of long-range order and the inherently statistical nature of its short-range order SRO. However, the local atomic arrangement of the nearest neighbors is expected to play an important role in the properties of liquid and amorphous materials. 2‐4 Recently, ab initio molecular dynamics MD simulations of the amorphous solids and liquid have provided profound insights into the structures and properties of these disordered materials, especially when the calculated data closely correspond to the experimental data. The consistency between the computer simulation and experimental data lends strong support to the further analysis of the structural and electronic properties of the amorphous or liquid systems. In this paper liquid structures of an Al60Cu40 alloy throughout a 450 K span of superheat temperature are studied both by experiments and ab initio MD simulations. The theoretical atomic configurations of the liquid structures are verified by comparing the calculated pair-correlation functions with the experimental results. The atomic configurations derived are further investigated using standard geometric methods. The local atomic structure of the liquid is then compared to various crystalline phases reported for Al-Cu alloys to check for topological similarities.

S. G. Hao

Papers

Experimental and ab initio molecular dynamics simulation studies of liquid Al 60 Cu 40 alloy