Universal self-assembly of one-component three-dimensional dodecagonal quasicrystals

Using molecular dynamics simulations, we study computational self-assembly of one-component three-dimensional dodecagonal (12-fold) quasicrystals in systems with two-length-scale potentials. Existing criteria for three-dimensional quasicrystal formation are quite complicated and rather inconvenient for particle simulations. So to localize numerically the quasicrystal phase, one should usually simulate over a wide range of system parameters. We show how to universally localize the parameters values at which dodecagonal quasicrystal order may appear for a given particle system. For that purpose, we use a criterion recently proposed for predicting decagonal quasicrystal formation in one-component two-length-scale systems. The criterion is based on two dimensionless effective parameters describing the fluid structure which are extracted from radial distribution function. The proposed method allows reducing the time spent for searching the parameters favoring certain solid structure for a given system. We show that the method works well for dodecagonal quasicrystals; this results is verified on four systems with different potentials: Dzugutov potential, oscillating potential which mimics metal interactions, repulsive shoulder potential describing effective interaction for core/shell model of colloids and embedded-atom model potential for aluminum. Our results suggest that mechanism of dodecagonal quasicrystal formation is universal for both metallic and soft-matter systems and it is based on competition between interparticle scales.Comment: 8 pages, 6 figure

Anomalous electrical conductivity in rapidly crystallized Cu50−x{}_{50-x}Zrx{}_{x} (x = 50 - 66.6) alloys

Cu${}_{50-x}$Zr${}_{x}$ (x = 50, 54, 60 and 66.6) polycrystalline alloys were prepared by arc-melting. The crystal structure of the ingots has been examined by X-ray diffraction. Non-equilibrium martensitic phases with monoclinic structure were detected in all the alloys except Cu${}_{33.4}$Zr${}_{66.6}$. Temperature dependencies of electrical resistivity in the temperature range of T = 4 - 300 K have been measured as well as room temperature values of Hall coefficients and thermal conductivity. Electrical resistivity demonstrates anomalous behavior. At the temperatures lower than 20 K, their temperature dependencies are non-monotonous with pronounced minima. At elevated temperatures they have sufficiently non-linear character which cannot be described within framework of the standard Bloch--Gr\"{u}neisen model. We propose generalized Bloch--Gr\"{u}neisen model with variable Debye temperature which describes experimental resistivity dependencies with high accuracy. We found that both the electrical resistivity and the Hall coefficients reveal metallic-type conductivity in the Cu-Zr alloys. The estimated values of both the charge carrier mobility and the phonon contribution to thermal and electric conductivity indicate the strong lattice defects and structure disorder.Comment: 6 pages, 3 figure

Can we accurately calculate viscosity in multicomponent metallic melts?

Calculating viscosity in multicompoinent metallic melts is a challenging task for both classical and \textit{ab~initio} molecular dynamics simulations methods. The former may not to provide enough accuracy and the latter is too resources demanding. Machine learning potentials provide optimal balance between accuracy and computational efficiency and so seem very promising to solve this problem. Here we address simulating kinematic viscosity in ternary Al-Cu-Ni melts with using deep neural network potentials (DP) as implemented in the DeePMD-kit. We calculate both concentration and temperature dependencies of kinematic viscosity in Al-Cu-Ni and conclude that the developed potential allows one to simulate viscosity with high accuracy; the deviation from experimental data does not exceed 9\% and is close to the uncertainty interval of experimental data. More importantly, our simulations reproduce minimum on concentration dependency of the viscosity at the eutectic point. Thus, we conclude that DP-based MD simulations is highly promising way to calculate viscosity in multicomponent metallic melts.Comment: 11 pages, 7 figure

Effective Pair Interactions and Structure in Liquid Noble Metals within Wills-Harrison and Bretonnet-Silbert Models

Recently, for calculating the effective pair interactions in liquid transition metals, we have developed an approach which includes the Wills-Harrison and Bretonnet-Silbert models as limit cases. Here, we apply this approach to noble liquid metals. The dependencies of pair potentials and corresponding MD-simulated pair correlation functions in pure liquid Cu, Ag and Au on the portion of the non-diagonal (with respect to the magnet quantum number) d-d-electron couplings in the metal under consideration are studied. The model provides a good agreement with experimental and ab initio data for pair correlation functions, structure factors and velocity autocorrelation functions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work is supported by the Russian Federation Ministry of Science and Higher Education through the state research target for the Institute of Metallurgy of the Ural Branch of Russian Academy of Sciences (Project No. 0396-2019-0002)

Structure and glass-forming ability of simulated Ni-Zr alloys

Binary Cu-Zr system is a representative bulk glassformer demonstrating high glass forming ability due to pronounced icosahedral local ordering. From the first glance, Ni-Zr system is the most natural object to expect the same behavior because nickel and copper are neighbours in the periodic table and have similar physicochemical properties. However, doing molecular dynamics simulations of $\rm Ni_{\alpha}Zr_{1-\alpha}$ alloys described by embedded atom model potential, we observe different behaviour. We conclude that the Ni-Zr system has the same glass-forming ability as an additive binary Lennard-Jones mixture without any chemical interaction. The structural analysis reveals that icosahedral ordering in Ni-Zr alloys is much less pronounced than that in the Cu-Zr ones. We suggest that lack of icosahedral ordering due to peculiarities of interatomic interactions is the reason of relatively poor glass-forming ability of Ni-Zr system