Metastable isomorphous phase diagram of the peritectic Ni-Ru system predicted byab initioand molecular dynamics calculations

Abstract

With the aid of ab initio calculation, an n-body potential of the equilibrium peritectic Ni-Ru (fcc-hcp) system is derived under the second-moment approximation of the tight-binding formalism. The derived Ni-Ru potential is proven to be relevant not only in reproducing some static properties, such as the cohesive energies and elastic constants, etc., also in reproducing some dynamic properties, such as the melting points and thermalexpansion coefficients, etc. Applying the proven realistic Ni-Ru potential, molecular dynamics simulations show that a crystalline solid solution of either fcc or hcp structure would always win while competing with its amorphous counterpart over the entire composition range, predicting that under a nonequilibrium condition, the Ni-Ru system may feature an isomorphous phase diagram, i.e., predicting a hardly glass-forming ability of the Ni-Ru system, which, however, was previously defined as a possibly glass-forming system. Interestingly, the prediction is in good agreement with the fact that no amorphous Ni-Ru alloy has so far been obtained by any glass-producing technique as well as with that deduced from the thermodynamic calculations. Besides, the present calculations demonstrate the possibility for an equilibrium fcc-hcp system to have a metastable isomorphous phase diagram, implying that a part of the previously defined possibly glass-forming systems may convert into the hardly glass-forming ones.

Atomistic modeling of epitaxial graphene on Ru(0001) and deposited ruthenium nanoparticles

“…It has been parametrized for a number of combined elements such as C-H [45], Pt-C [53], Si-C [63], Zn-O [64], Fe-C [65], and even Be-C-W-H [66], among others. It naturally includes many-body contributions for metals in the second moment approximation to the tight-binding scheme (TB-SMA) [67], which have notably been parametrized for ruthenium [48][49][50]. The BOP framework was thus naturally chosen to model the system of interest here, namely, epitaxial graphene on Ru(0001) and Ru nanoparticles deposited on carbon substrates.…”

“…Our potential combines the bondorder potential (BOP) for carbon developed by Brenner [45] with an embedded-atom model (EAM) for ruthenium. Among the various existing EAM models for this metal [46][47][48][49][50][51], we have chosen the form and parameters by Li and coworkers [48][49][50] that can be rewritten under the BOP format [52], providing a uniform and simple expression for the general Ru-C potential, similar to previous efforts carried by Albe and coworkers for the Pt-C system [53]. In order not to degrade those original potentials for the pure elements, only the parameters corresponding to mixed Ru-C interactions were adjusted in order to reproduce available electronic structure data [38,44].…”

Proposed Definition of Microchemical Inhomogeneity and Application To Characterize Some Selected Miscible/Immiscible Binary Metal Systems

“…In other words, there exists almost no tendency of ordering or clustering in the system. The calculated MCI could also account for the fact that the Ni−Ru system is a hardly glass-forming one and that no amorphous alloy has so far been obtained in the system by any currently available glass-producing techniques …”

“…As mentioned above, the Ni-Ru system has a small positive heat of mixing (about +1.5 kJ/mol), and according to a recent study by the present authors, nickel and ruthenium may form a metastable isomorphous phase diagram under a nonequilibrium state. 36 As a result, the amorphous alloy is hardly formed in the Ni-Ru system, which could therefore be classified as a hardly glass-forming system. In contrast, the Ni-Hf system, due to its large negative heat of mixing (about -63 kJ/mol), is classified as a readily glass-forming system.…”

Atomistic Modeling of Crystal-to-Amorphous Transition and Associated Kinetics in the Ni−Nb System by Molecular Dynamics Simulations

“…In the early 1980s, a powerful method, that is, ion beam mixing (IBM) of multiple metal layers, was developed, and numerous amorphous alloys have since been produced in a great number of binary metal systems to date. Because of its high capability, IBM is even able to produce metallic glasses in some equilibrium immiscible systems, in which LMQ is not able to co-melt the two constituent metals to form any alloy, , yet has so far not succeeded in obtaining amorphous alloys in some other systems, for example, the Ni−Ru system, which has a peritectic phase diagram at equilibrium …”