Reactive cluster model of metallic glasses

Jones, Travis E.; Miorelli, Jonathan; Eberhart, Mark E.

doi:10.1063/1.4865336

Cited by 13 publications

(3 citation statements)

References 53 publications

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“…The challenge is identifying the relevant topological units and then cataloging the possible interactions between these units. As an example, we previously brought this methodology to bear in a study of the structure of metallic glasses [ 53 ]. Though complex and confronted with difficulties, the approach allows for a more direct application of chemical formalism.…”

Section: Discussionmentioning

confidence: 99%

Principles Determining the Structure of Transition Metals

et al. 2021

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For the better part of a century researchers across disciplines have sought to explain the crystallography of the elemental transition metals: hexagonal close packed, body centered cubic, and face centered cubic in a form similar to that used to rationalize the structure of organic molecules and inorganic complexes. Pauling himself tried with limited success to address the origins of transition metal stability. These early investigators were handicapped, however, by incomplete knowledge regarding the structure of metallic electron density. Here, we exploit modern approaches to electron density analysis to first comprehensively describe transition metal electron density. Then, we use topological partitioning and quantum mechanically rigorous treatments of kinetic energy to account for the structure of the density as arising from the interactions between metallic polyhedra. We argue that the crystallography of the early transition metals results from charge transfer from the so called “octahedral” to “tetrahedral cages” while the face centered cubic structure of the late transition metals is a consequence of anti-bonding interactions that increase octahedral hole kinetic energy.

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Section: Discussionmentioning

confidence: 99%

Principles Determining the Structure of Transition Metals

et al. 2021

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“…These clusters can be treated as Jahn-Teller units with d-orbitals being the highest occupied molecular orbitals. These Jahn-Teller units distort and orient in random directions [47]. Figure 4 shows some of the possible Jahn-Teller distortions of an icosahedral molecular unit.…”

Section: Discussionmentioning

confidence: 99%

Cooperative Jahn–Teller phase transition of icosahedral molecular units

Nasrollahi¹,

Vvedensky²

2016

J. Phys.: Condens. Matter

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Non-linear molecules undergo distortions when the orbital degeneracy of the highest occupied level is lifted by the Jahn-Teller effect. If such molecules or clusters of atoms are coupled to one another, the system may experience a cooperative Jahn-Teller effect (CJTE). In this paper, we describe a model of how the CJTE leads to the crystallization of the disordered phase. The model Hamiltonian is based on a normal mode decomposition of the clusters in order to maintain the symmetry labels. We take account of the electron-strain and the electron-phonon couplings and, by displacing the coordinates of the oscillators, obtain a term that explicitly couples the Jahn-Teller centers, enabling us to perform a mean-field analysis. The calculation of the free energy then becomes straightforward, and obtaining phase diagrams in various regimes follows from the minimization of this free energy. The results show that the character of the phase transition may change from strong to weak first order and even to second-order, depending on the coupling to the vibrational modes. Taken together, these results may serve as a paradigm for crystallization near the transition temperature, where the atoms tend to form clusters of icosahedral symmetry.

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“…In this case, the structural characteristics of CMAs cannot be reflected through the crystallographic method, not to mention their structure-related properties 8 9 10 . Since the atomic clusters are advocated as primary units to represent materials’ structural features, to solve the above problem, various cluster-based models have been developed during the past decades 11 12 13 14 15 16 17 . Among these cluster-based models, Dong’s “cluster-plus-glue-atom” model 15 can be used to describe the atomic structure of nearly all materials.…”

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confidence: 99%

Hidden electronic rule in the “cluster-plus-glue-atom” model

Chen

Melnik

et al. 2016

Sci Rep

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Electrons and their interactions are intrinsic factors to affect the structure and properties of materials. Based on the “cluster-cluster-plus-glue-atom” model, an electron counting rule for complex metallic alloys (CMAs) has been revealed in this work (i. e. the CPGAMEC rule). Our results on the cluster structure and electron concentration of CMAs with apparent cluster features, indicate that the valence electrons’ number per unit cluster formula for these CMAs are specific constants of eight-multiples and twelve-multiples. It is thus termed as specific electrons cluster formula. This CPGAMEC rule has been demonstrated as a useful guidance to direct the design of CMAs with desired properties, while its practical applications and underlying mechanism have been illustrated on the basis of CMAs’ cluster structural features. Our investigation provides an aggregate picture with intriguing electronic rule and atomic structural features of CMAs.

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Reactive cluster model of metallic glasses

Cited by 13 publications

References 53 publications

Principles Determining the Structure of Transition Metals

Principles Determining the Structure of Transition Metals

Cooperative Jahn–Teller phase transition of icosahedral molecular units

Hidden electronic rule in the “cluster-plus-glue-atom” model

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