Kim, GeunwooYamada, RyoTakaki, TomohiroShibuta, Yasushi...
9页
查看更多>>摘要：A machine leaning-based approach is proposed for the inverse analysis of the anisotropy parameters of solid -liquid interfacial free energy. The interface shape distribution (ISD) map, which characterizes the details of the dendrite morphology, was selected as the input of a convolutional neural network (CNN). The ISD maps for a free-growing dendrite during the isothermal solidification of a model alloy system were obtained by quantitative phase-field simulations and used as the training and test data for the CNN. Two anisotropy parameters were estimated with errors of less than 5%, which can be further improved by increasing the size of the training dataset.
查看更多>>摘要：The study of the properties of defects in silicon forming under irradiation condition has been carried out for many years, however, many open questions remain. Particularly, there are not comprehensive results for variety of radiation centers calculated at the same level of theory. For example the previously calculated transition levels and formation energies show a large scatter. In this work, we focus on the important radiation-induced defect complexes in Si: double vacancy, vacancy-oxygen, vacancy-phosphorus. Additionally, the phosphorus-vacancy-oxygen complex was studied. Formation energy, charge transition levels and binding energy were calculated from first-principles using the hybrid exchange-correlation functional HSE06. Spin polarized calculations and large supercells allows us to obtain charge transition levels which agree well with experimental measurements.
查看更多>>摘要：Block copolymers consisting of immiscible glassy and rubbery blocks have microphase-separated structures that result in various elastic properties depending on the polymer structures. However, because the complete simulation approach to surveying a wide variety of polymer and microphase-separated structures is time-consuming, a more efficient approach is required for the design of materials with desired properties. In the present study, we used coarse-grained molecular dynamics (CGMD) simulations and an artificial neural network (ANN) to design polymer structures with the desired stress-strain properties. CGMD simulations were conducted to obtain stress-strain curves of linear diblock and triblock copolymers of various chain lengths, block volume fractions, and asymmetricities. We trained the ANN for regression between the polymer structures and the stress-strain curves. Then, using the trained ANN, we performed Bayesian optimization to obtain a polymer structure with an arbitrary target stress-strain curve. CGMD simulations of the optimized polymer structure produced a stress-strain curve that agreed with the curve predicted by the ANN. Therefore, simulation and use of an ANN are potentially useful strategies for the design of polymer structures with desired properties.
查看更多>>摘要：Honeycomb layered tellurates represent a burgeoning class of multi-functional materials with fascinating crystal-structural versatility and a rich composition space. Despite their multifold capabilities, their compositional di-versity remains underexplored due to complexities in experimental design and syntheses. Thus, in a bid to expand this frontier and derive relevant insights into allowed metastable compositions, we employ a density functional theory (DFT) approach to predict in silico the crystal structures of new honeycomb layered tellurates embodied by the composition, A(2)Ni(2)TeO(6) (A = alkali, hydrogen or coinage-metal cations). Here, alkali-metal atoms with vastly larger radii than K (for instance, Rb and Cs) are found to engender a prismatic coordination with the oxygen atoms from the honeycomb slabs whilst coinage-metal atoms (such as Ag, Au and Cu) display a propensity for linear coordination. Further, H2Ni2TeO6 is found to also render a linear coordination wherein the hydrogen atom preferentially establishes a stronger coordination with one of the oxygen atoms to form hydroxyl groups. All A cations in the studied & nbsp;A(2)Ni(2)TeO(6) compositions form a honeycomb lattice. Conclusions on the possibility of a monolayer-bilayer phase transition in coinage metal atom tellurates can be drawn by considering the implications of conformal symmetry of the cation honeycomb lattice and metallophilicity. This work not only propounds new honeycomb layered tellurate compositions but also provides novel insight into the rational design of multifunctional materials for applications ranging from energy storage, catalysis and optics to analogue condensed matter systems of gravity.
查看更多>>摘要：We present a guide to compute the phase-boundaries of classical systems using a dynamic Clausius-Clapeyron integration (dCCI) method within the LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) code. The advantage of the dCCI method is because it provides coexistence curves spanning a wide range of thermodynamic states using relatively short single non-equilibrium simulations. We describe the state-of-the-art of non-equilibrium free-energy methods that allow us to compute the Gibbs free-energy in a wide interval of pressure and/or temperature. We present the dCCI method in details, discuss its implementation in the LAMMPS package and make available source code, scripts, as well as auxiliary files. As an illustrative example, we determine the phase diagram of silicon in a range of pressures covering from 0 to 15 GPa and temperatures as low as 400 K up to the liquid phase, in order to obtain the phase boundaries and triple point between diamond, liquid and beta-Sn phases.
查看更多>>摘要：In this study, a novel modeling approach for gas permeability prediction has been proposed. For the first time, simultaneous effects of particle agglomeration and interfacial layer have been considered directly in the model formula. The results show that the model fits well with the experimental data due to considering both particle agglomeration and interfacial shell layer. For instance, average absolute relative error (AARE) has been decreased from 51% to 0.73% for O-2 permeability through polyethersulfone (PES)/Zeolite 4A mixed matrix membrane (MMM). Also, the precision of the proposed model is nearly more than 95% for all the studied cases showing the great potential of this model in the prediction of MMMs permeability. The output of this study will help chemical engineers to fabricate MMMs with optimal permeability and selectivity and to get a better insight into particle-particle and particle-polymer interactions.
查看更多>>摘要：Most of the lattice Boltzmann methods simulate an approximation of the sharp interface problem of dissolution and precipitation. In such studies the curvature-driven motion of interface is neglected in the Gibbs-Thomson condition. In order to simulate those phenomena with or without curvature-driven motion, we propose a phase-field model which is derived from a thermodynamic functional of grand-potential. Compared to the free energy, the main advantage of the grand-potential is to provide a theoretical framework which is consistent with the equilibrium properties such as the equality of chemical potentials. The model is composed of one equation for the phase-field phi coupled with one equation for the chemical potential mu. In the phase-field method, the curvature-driven motion is always contained in the phase-field equation. For canceling it, a counter term must be added in the phi-equation. For reason of mass conservation, the mu-equation is written with a mixed formulation which involves the composition c and the chemical potential. The closure relationship between c and mu is derived by assuming quadratic free energies for the bulk phases. The anti-trapping current is also considered in the composition equation for simulations with null solid diffusion. The lattice Boltzmann schemes are implemented in LBM_saclay, a numerical code running on various High Performance Computing architectures. Validations are carried out with analytical solutions representative of dissolution and precipitation. Simulations with or without counter term are compared on the shape of porous medium characterized by microtomography. The computations have run on a single GPU-V100.
查看更多>>摘要：The thermal conductivities kappa of wurtzite InxGa1-xN are investigated using equilibrium molecular dynamics (MD) method. The kappa of InxGa1-xN rapidly declines from InN (kappa InN = 141 W/mK) or GaN (kappa GaN = 500 W/mK) to InxGa1-xN (x =/ or 1), and reaches a minimum (kappa min = 19 W/mK) when xis around 0.5 at 300 K. The mean free path (MFP) of InxGa1-xN, ranging from 2 to 5 nm and following the same trend with the kappa, is extrapolated in our simulation and a parabolic relationship between x and MFP is established. We find that the kappa of InxGa1-xN decreases with increasing temperatures. The evolution of kappa of InxGa1-xN is also examined by projecting the momentum-energy relationship of phonons from MD trajectories. The phonon dispersion and phonon density of states for InxGa1-xN reflect a slightly more flattened dispersive phononic curve of the alloying system. Despite an overestimated kappa than experimental values, our calculated kappa at 300 K agrees well with the results obtained by solving Boltzmann transport equation and also has the same stoichiometric trend with the experimental data. Our study provides the coherent analysis of the effect of thickness, temperature and stoichiometric content on the thermal transport of InxGa1-xN which is helpful for the thermal management of InxGa1-xN based devices.
NSTL
Elsevier