Anomalous thermal contraction of the first coordination shell in metallic alloy liquids

Gangopadhyay, A. K.; Blodgett, M.; Johnson, Mark L.; McKnight, John; Wessels, V.; Vogt, Adam; Mauro, N. A.; Bendert, J. C.; Soklaski, Ryan; Yang, Li; Kelton, K. F.

doi:10.1063/1.4861666

Cited by 32 publications

(22 citation statements)

References 33 publications

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“…5a), giving an anomalous negative thermal expansion. Similar behavior has been reported in the first shell of g(r)s that were obtained from experimental measurements [28][29][30]. It appears to be partially the result of an increasing first-shell coordination number with decreasing temperature, leading to a weakening of the bond strengths in the first shell as the valence electrons are shared among more atoms.…”

Section: Resultssupporting

confidence: 71%

Estimated partial pair correlation functions in Cu–Zr liquids

Blodgett

Kelton

2015

Journal of Non-Crystalline Solids

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a b s t r a c tWhile X-ray scattering studies can provide some insight into the average topological structures of liquids, they provide limited information on chemical ordering. Combined X-ray and neutron scattering studies can address this limitation, but are often difficult, time consuming and expensive, if isotopes are used for the neutron scattering measurements. Further, it is extremely difficult to make neutron scattering studies of reactive liquids like the Zr-based alloys of interest as metallic glass formers, particularly in the supercooled state. Here, a method for obtaining some chemical information that was applied previously to Cu-Zr glasses is used to obtain estimates of the partial pair correlation functions of their liquids. X-ray scattering data from Cu-Zr liquids with a range of chemical combinations are combined with molecular dynamics study results for one composition to consistently construct the partial pair correlations. The total pair correlation functions calculated using these partials agree well with the experimental data.

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Section: Resultssupporting

confidence: 71%

Estimated partial pair correlation functions in Cu–Zr liquids

Blodgett

Kelton

2015

Journal of Non-Crystalline Solids

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“…Specifically, the coordination polyhedron changes to a denser one with a reduced coordination number and a shorter bond length (distance between the center atom and atoms in the first nearest-neighbor shell). In a later report, Gangopadhyay et al 34 also observed similar anomalous shift of the first peak for a number of alloy liquids (but not without obvious exceptions).…”

Section: Introductionmentioning

confidence: 62%

“…An intriguing behavior noticed in recent studies is an anomalous temperature dependence of the first peak position in the atomic PDFs, g(r), of metallic liquids: [33][34][35]71 the position (distance r) corresponding to the maximum intensity of the first peak shifts towards shorter r with increasing temperature (see Fig. 4).…”

Section: Introductionmentioning

confidence: 99%

“…Examples include a structural signature of dynamical slowdown as well as the liquid fragility in metallic glass-forming liquids, [26][27][28][29][30][31][32] anomalous thermal contraction of metallic melts in the nearest-neighbor shell, [33][34][35] possible crystallike order in MGs/liquids, [36][37][38][39] a fractal structure model of MGs, [40][41][42] advanced algorithms (such as machine learning methods) to efficiently characterize the structural basis of flow defects and dynamical slowdown in amorphous materials, 43,44 and a new structure parameter that incorporates dynamic (atomic vibration) information beyond the description of static structure/ configuration. [45][46][47][48][49] Computational research has played a key role in formulating these ideas.…”

Section: Introductionmentioning

confidence: 99%

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Computational modeling sheds light on structural evolution in metallic glasses and supercooled liquids

Ding

2017

npj Comput Mater

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This article presents an overview of three challenging issues that are currently being debated in the community researching on the evolution of amorphous structures in metallic glasses and their parent supercooled liquids. Our emphasis is on the valuable insights acquired in recent computational analyses that have supplemented experimental investigations. The first idea is to use the local structural order developed, and in particular its evolution during undercooling, as a signature indicator to rationalize the experimentally observed temperature-dependence of viscosity, hence suggesting a possible structural origin of liquid fragility. The second issue concerns with the claim that the average nearest-neighbor distance in metallic melts contracts rather than expands upon heating, concurrent with a reduced coordination number. This postulate is, however, based on the shift of the first peak maximum in the pair distribution function and an average bond length determined from nearest neighbors designated using a distance cutoff. These can instead be a result of increasing skewness of the broad first peak, upon thermally exacerbated asymmetric distribution of neighboring atoms activated to shorter and longer distances under the anharmonic interatomic interaction potential. The third topic deals with crystal-like peak positions in the pair distribution function of metallic glasses. These peak locations can be explained using various connection schemes of coordination polyhedra, and found to be present already in high-temperature liquids without hidden crystal order. We also present an outlook to invite more in-depth computational research to fully settle these issues in future, and to establish more robust structure-property relations in amorphous alloys.npj Computational Materials (2017) 3:9 ;

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“…expansion, shifting towards larger r with decreasing temperature. This is now emerging as common behavior, reported in many metallic glass-forming liquids [51,52]. The character of the first peak in g(r) for the different glasses is one of the more interesting features (Fig.…”

Section: Resultsmentioning

confidence: 94%

Structural evolution and thermophysical properties of ZrxNi100−x metallic liquids and glasses

Johnson

Mauro

Vogt

et al. 2014

Journal of Non-Crystalline Solids

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The results of high-energy X-ray scattering studies over a wide temperature range for equilibrium and supercooled Zr x Ni 100 − x (x = 36, 57, 76) liquids and the corresponding glasses are presented. The results of liquid density and viscosity measurements are also shown. All of the liquid studies were made on containerlessly processed liquids using the technique of electrostatic levitation. The scattering data were used to determine the temperature-dependent total structure factor, S(q), and pair-correlation function, g(r). A discontinuity is observed between the magnitude of the first peak in S(q) of the liquid when extrapolated to the glass transition temperature, T g , and the value determined for the structurally relaxed glass at T g . This indicates that the structural ordering in the liquid accelerates upon approaching T g , consistent with the behavior expected for a fragile liquid. An asymmetry in the first peak in the pair correlation function develops with decreasing temperature for all alloy liquids and glasses, suggesting that chemical ordering accompanies the structural ordering.

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Anomalous thermal contraction of the first coordination shell in metallic alloy liquids

Cited by 32 publications

References 33 publications

Estimated partial pair correlation functions in Cu–Zr liquids

Estimated partial pair correlation functions in Cu–Zr liquids

Computational modeling sheds light on structural evolution in metallic glasses and supercooled liquids

Structural evolution and thermophysical properties of ZrxNi100−x metallic liquids and glasses

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