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Second-Nearest-Neighbor Correlations from Connection of Atomic Packing Motifs in Metallic Glasses and Liquids.

Ding J, Ma E, Asta M, Ritchie RO - Sci Rep (2015)

Bottom Line: The analysis was conducted from the perspective of different connection schemes of atomic packing motifs, based on the number of shared atoms between two linked coordination polyhedra.These properties of the connections and the resultant atomic correlations are generally the same for different types of packing motifs in different alloys.Increasing ordering and cluster connection during cooling, however, may tune the position and intensity of the split peaks.

View Article: PubMed Central - PubMed

Affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

ABSTRACT
Using molecular dynamics simulations, we have studied the atomic correlations characterizing the second peak in the radial distribution function (RDF) of metallic glasses and liquids. The analysis was conducted from the perspective of different connection schemes of atomic packing motifs, based on the number of shared atoms between two linked coordination polyhedra. The results demonstrate that the cluster connections by face-sharing, specifically with three common atoms, are most favored when transitioning from the liquid to glassy state, and exhibit the stiffest elastic response during shear deformation. These properties of the connections and the resultant atomic correlations are generally the same for different types of packing motifs in different alloys. Splitting of the second RDF peak was observed for the inherent structure of the equilibrium liquid, originating solely from cluster connections; this trait can then be inherited in the metallic glass formed via subsequent quenching of the parent liquid through the glass transition, in the absence of any additional type of local structural order. Increasing ordering and cluster connection during cooling, however, may tune the position and intensity of the split peaks.

No MeSH data available.


Related in: MedlinePlus

The relation between cluster shear strains, γcluster, of different cluster connection schemes in terms of the imposed macroscopic shear strain γimposed for samples #1 to 8 in Table 1.The dashed line indicates where the cluster strains are equal to the imposed macroscopic shear strains.
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f5: The relation between cluster shear strains, γcluster, of different cluster connection schemes in terms of the imposed macroscopic shear strain γimposed for samples #1 to 8 in Table 1.The dashed line indicates where the cluster strains are equal to the imposed macroscopic shear strains.

Mentions: Unlike crystalline metals, the elastic deformation of MGs is intrinsically inhomogeneous due to the wide variation in the local structural arrangements282950515253. Consequently, it is interesting to examine the elastic response with respect to different atomic cluster connections within amorphous solids. Here we use MD simulations to examine the athermal quasi-static shear (AQS)54 deformation of samples #1 to 8 in Table 1 in the nominally elastic regime; we further calculate elastic strains generated between connected coordination polyhedra (calculations are described in the Methods section). In Fig. 5, we plot the average elastic shear strain for each group of cluster connection schemes (colored arrows) in comparison to the imposed macroscopic shear strain; the dashed line in the figure represents where cluster strain equals the imposed macroscopic strain. We observe that i) the elastic strain experienced by clusters connected via the 1-atom classification is almost equivalent to that of the macroscopic deformation; ii) the elastic responses of clusters with both the 2-atom and 4-atom connections behave in a more flexible manner (i.e., they show deformation larger than the macroscopic strain) while clusters with 3-atom connections are the stiffest (i.e., they show the smallest local shear strain). Sharing of triangulated faces between tetrahedra is likely to result in higher energy barrier W of basins in the potential energy landscape, which is known to increase shear modulus G5556.


Second-Nearest-Neighbor Correlations from Connection of Atomic Packing Motifs in Metallic Glasses and Liquids.

Ding J, Ma E, Asta M, Ritchie RO - Sci Rep (2015)

The relation between cluster shear strains, γcluster, of different cluster connection schemes in terms of the imposed macroscopic shear strain γimposed for samples #1 to 8 in Table 1.The dashed line indicates where the cluster strains are equal to the imposed macroscopic shear strains.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663502&req=5

f5: The relation between cluster shear strains, γcluster, of different cluster connection schemes in terms of the imposed macroscopic shear strain γimposed for samples #1 to 8 in Table 1.The dashed line indicates where the cluster strains are equal to the imposed macroscopic shear strains.
Mentions: Unlike crystalline metals, the elastic deformation of MGs is intrinsically inhomogeneous due to the wide variation in the local structural arrangements282950515253. Consequently, it is interesting to examine the elastic response with respect to different atomic cluster connections within amorphous solids. Here we use MD simulations to examine the athermal quasi-static shear (AQS)54 deformation of samples #1 to 8 in Table 1 in the nominally elastic regime; we further calculate elastic strains generated between connected coordination polyhedra (calculations are described in the Methods section). In Fig. 5, we plot the average elastic shear strain for each group of cluster connection schemes (colored arrows) in comparison to the imposed macroscopic shear strain; the dashed line in the figure represents where cluster strain equals the imposed macroscopic strain. We observe that i) the elastic strain experienced by clusters connected via the 1-atom classification is almost equivalent to that of the macroscopic deformation; ii) the elastic responses of clusters with both the 2-atom and 4-atom connections behave in a more flexible manner (i.e., they show deformation larger than the macroscopic strain) while clusters with 3-atom connections are the stiffest (i.e., they show the smallest local shear strain). Sharing of triangulated faces between tetrahedra is likely to result in higher energy barrier W of basins in the potential energy landscape, which is known to increase shear modulus G5556.

Bottom Line: The analysis was conducted from the perspective of different connection schemes of atomic packing motifs, based on the number of shared atoms between two linked coordination polyhedra.These properties of the connections and the resultant atomic correlations are generally the same for different types of packing motifs in different alloys.Increasing ordering and cluster connection during cooling, however, may tune the position and intensity of the split peaks.

View Article: PubMed Central - PubMed

Affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

ABSTRACT
Using molecular dynamics simulations, we have studied the atomic correlations characterizing the second peak in the radial distribution function (RDF) of metallic glasses and liquids. The analysis was conducted from the perspective of different connection schemes of atomic packing motifs, based on the number of shared atoms between two linked coordination polyhedra. The results demonstrate that the cluster connections by face-sharing, specifically with three common atoms, are most favored when transitioning from the liquid to glassy state, and exhibit the stiffest elastic response during shear deformation. These properties of the connections and the resultant atomic correlations are generally the same for different types of packing motifs in different alloys. Splitting of the second RDF peak was observed for the inherent structure of the equilibrium liquid, originating solely from cluster connections; this trait can then be inherited in the metallic glass formed via subsequent quenching of the parent liquid through the glass transition, in the absence of any additional type of local structural order. Increasing ordering and cluster connection during cooling, however, may tune the position and intensity of the split peaks.

No MeSH data available.


Related in: MedlinePlus