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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

(a) The number of connected clusters per atom, N, for four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) at room temperature (T=300 K) for samples #1 to 8 in Table 1. (b) The difference in N for each of the four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) between T = 300 K and the liquidus temperature for sample #1 to 8 in Table 1. The first four samples as marked, are Cu64Zr36 MGs prepared at increasing cooling rates.
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f4: (a) The number of connected clusters per atom, N, for four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) at room temperature (T=300 K) for samples #1 to 8 in Table 1. (b) The difference in N for each of the four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) between T = 300 K and the liquidus temperature for sample #1 to 8 in Table 1. The first four samples as marked, are Cu64Zr36 MGs prepared at increasing cooling rates.

Mentions: Another important issue is if and how the cluster connections depend on the nearest-neighbor coordination number (CN). The CN varies with the local SRO, reflecting different atomic size ratio and cluster topological order for each amorphous system. In other words, the packing motif is different from alloy to alloy. This issue is examined in Fig. 3(b), where we plot the average number of cluster connections against the average CN surrounding each species, in various alloys (Table 1) at the corresponding experimental liquidus temperatures (Tl)46. The largest NN coordination number is for La atoms in Al90La10, since La atoms are much larger than Al. Although the experimental value of Tl may not correspond exactly with the liquidus predicted by the EAM potential, we have also tested the temperature range between (Tl  − 100) K and (Tl  + 100) K, and the results in Fig. 3(b) are largely unaffected. Analysis at the liquidus temperatures undertaken here avoids the complexity associated with cluster connection development by structural ordering during cooling through the glass transition (illustrated in detail below in Fig. 4).


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)

(a) The number of connected clusters per atom, N, for four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) at room temperature (T=300 K) for samples #1 to 8 in Table 1. (b) The difference in N for each of the four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) between T = 300 K and the liquidus temperature for sample #1 to 8 in Table 1. The first four samples as marked, are Cu64Zr36 MGs prepared at increasing cooling rates.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: (a) The number of connected clusters per atom, N, for four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) at room temperature (T=300 K) for samples #1 to 8 in Table 1. (b) The difference in N for each of the four cluster connection schemes (1-atom, 2-atom, 3-atom and 4-atom) between T = 300 K and the liquidus temperature for sample #1 to 8 in Table 1. The first four samples as marked, are Cu64Zr36 MGs prepared at increasing cooling rates.
Mentions: Another important issue is if and how the cluster connections depend on the nearest-neighbor coordination number (CN). The CN varies with the local SRO, reflecting different atomic size ratio and cluster topological order for each amorphous system. In other words, the packing motif is different from alloy to alloy. This issue is examined in Fig. 3(b), where we plot the average number of cluster connections against the average CN surrounding each species, in various alloys (Table 1) at the corresponding experimental liquidus temperatures (Tl)46. The largest NN coordination number is for La atoms in Al90La10, since La atoms are much larger than Al. Although the experimental value of Tl may not correspond exactly with the liquidus predicted by the EAM potential, we have also tested the temperature range between (Tl  − 100) K and (Tl  + 100) K, and the results in Fig. 3(b) are largely unaffected. Analysis at the liquidus temperatures undertaken here avoids the complexity associated with cluster connection development by structural ordering during cooling through the glass transition (illustrated in detail below in Fig. 4).

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