The origin of broadband blue emission in zero-dimensional organic lead iodine perovskites: A first-principles study.

Broadband blue emission in zero-dimensional perovskites has received considerable attention, which is very important for the realization of stable blue-light emitters; however, the underlying formation mechanism remains unclear. Based on first-principles calculations, we have systematically studied the self-trapped excitons (STEs) behavior and luminescence properties in 0D-(DMA)4PbI6 perovskite. Our calculations show that there is a significant difference between the intrinsic STE luminescence mechanism (∼2.

Pattern Formation under Deep Supercooling by Classical Density Functional-Based Approach.

Solidification patterns during nonequilibrium crystallization are among the most important microstructures in the natural and technical realms. In this work, we investigate the crystal growth in deeply supercooled liquid using the classical density functional-based approaches. Our result shows that the complex amplitude expanded phase-field crystal (APFC) model containing the vacancy nonequilibrium effects proposed by us could naturally reproduce the growth front nucleation (GFN) and various nonequilibrium patterns, including the faceted growth, spherulite, symmetric and nonsymmetric dendrites among others, at the atom level.

Shock-induced plasticity and phase transformation in single crystal magnesium: an interatomic potential and non-equilibrium molecular dynamics simulations.

An effective and reliable Finnis-Sinclair (FS) type potential is developed for large-scale molecular dynamics (MD) simulations of plasticity and phase transition of magnesium (Mg) single crystals under high-pressure shock loading. The shock-wave profiles exhibit a split elastic-inelastic wave in the [0001]shock orientation and a three-wave structure in the [10-10]and [-12-10]directions, namely, an elastic precursor, a followed plastic front, and a phase-transition front. The shock Hugoniot of the particle velocity () vs the shock velocity () of Mg single crystals in three shock directions under low shock strength reveals apparent anisotropy, which vanishes with increasing shock strength.

Molecular dynamics simulations of shock loading of nearly fully dense granular Ni-Al composites.

We used molecular dynamics simulations to study the shock propagation, inhomogeneous deformation, and initiation of the chemical reaction characteristics of nearly fully dense reactive Ni-Al composites. For shocks with piston velocities Up ≤ 2.0 km s-1, particle velocity dispersion was observed at the shock front, which increased on increasing the shock strength.

Intrinsic strain-induced segregation in multiply twinned Cu-Pt icosahedra.

We present an atomistic simulation study on the compositional arrangements throughout Cu-Pt icosahedra, with a specific focus on the effects of inherent strain on general segregation trends. The coexistence of radial and site-selective segregation patterns is found in bimetallic nanoparticles for a broad range of sizes and compositions, consistent with prior analytical and atomistic models. Through a thorough comparison between the composition patterns and strain-related patterns, it is suggested that the presence of gradient and site-selective segregation is natural to largely relieve the inherent strain by preferential segregation of big atoms at tensile sites and vice versa, as previously hypothesized in the literature.

Effect of particle packing and density on shock response in ordered arrays of Ni + Al nanoparticles.

We investigate the shock response of Ni + Al reactive nanoparticle systems through molecular dynamics simulations. The powder configurations with varying arrangements and densities are constructed by stacking equal-sized Ni and Al particles based on five typical crystal structures, i.e.

Investigation of the shock-induced chemical reaction (SICR) in Ni + Al nanoparticle mixtures.

Molecular dynamics (MD) simulations are used to investigate the shock-compression response of Ni + Al spherical nanoparticles arranged in a NaCl-like structure. The deformation and reaction characteristics are studied from the particle level to the atomic scale at various piston velocities. Shock-induced chemical reactions (SICRs) occur during non-equilibrium processes, accompanied by a sharp rise in temperature and rapid mixing of atoms.

A new embedded-atom method approach based on the pth moment approximation.

Large scale atomistic simulations with suitable interatomic potentials are widely employed by scientists or engineers of different areas. The quick generation of high-quality interatomic potentials is urgently needed. This largely relies on the developments of potential construction methods and algorithms in this area.

Amorphization and thermal stability of aluminum-based nanoparticles prepared from the rapid cooling of nanodroplets: effect of iron addition.

Despite an intensive investigation on bimetallic nanoparticles, little attention has been paid to their amorphization in the past few decades. The study of amorphization on a nanoscale is of considerable significance for the preparation of amorphous nanoparticles and bulk metallic glass. Herein, we pursue the amorphization process of Al-based nanoparticles with classic molecular dynamics simulations and local structural analysis techniques.

Morphology, dimension, and composition dependence of thermodynamically preferred atomic arrangements in Ag-Pt nanoalloys.

The present article is on Metropolis Monte Carlo simulations coupled with semiempirical potentials to obtain the thermodynamically preferred configurations of Ag-Pt nanoalloys. The effects of particle size, morphology or alloy composition on the surface segregation and the chemical ordering patterns were investigated. Surface segregation of Ag is observed in all Ag-Pt nanoalloys.

Melting temperature of Pb nanostructural materials from free energy calculation.

The thermodynamic properties of lead, including the entropy, heat capacity, Gibbs free energy, and surface free energy have been studied. Based on bulk thermodynamic properties of lead, Gibbs free energy for nanostructural materials is obtained and used to calculate the size-dependent melting point depression for lead nanostructural materials. The studies indicate that the surface free energy difference between solid phase and liquid phase is a decisive factor for the size-dependent melting of nanostructural materials.

Melting temperature: from nanocrystalline to amorphous phase.

By extrapolating the mean grain size of nanocrystal to an infinitesimal value, an amorphous phase has been obtained from the Voronoi construction. The molecular dynamics simulations indicated that for nanocrystal, the grain size variation of melting temperature exhibits two characteristic regions. As mean grain size above about 4 nm for Ag, the melting temperatures decrease with decreasing grain size.

Comparative study of microstructural evolution during melting and crystallization.

Molecular dynamics simulations, with the interaction between atoms described by a modified analytic embedded atom method, have been performed to obtain the atomic-scale details of isothermal melting in nanocrystalline Ag and crystallization from supercooled liquid. The radial distribution function and common neighbor analysis provide a visible scenario of structural evolution in the process of phase transition. The results indicate that melting at a fixed temperature in nanocrystalline materials is a continuous process, which originates from the grain boundary network.

Melting behaviors of nanocrystalline Ag.

In the atomic scale, the melting behaviors of nanocrystalline Ag with mean grain size ranging from 3.03 to 12.12 nm have been investigated with molecular dynamics simulations, and a method to determine the melting temperatures of the infinite polycrystalline nanostructured materials is presented.

[Managements of masked mastoiditis].

Objective: To appreciate clinically of masked mastoiditis to explored how to reduce the incidence and associated morbidity of otogenic complications.

Methods: Between January 1998 and February 2005, 11 cases of masked mastoiditis were collected retrospectively. Their clinical presentation, results of investigations, and response to treatment were reviewed.

Shell and subshell periodic structures of icosahedral nickel nanoclusters.

Using the modified analytic embedded atom method and molecular dynamics, the binding energies and their second order finite differences (stability functions) of icosahedral Ni clusters with shell and subshell periodicity are studied in detail via atomic evolution. The results exhibit shell and subshell structures of the clusters with atoms from 147 to 250,000, and the atomic numbers corresponding to shell or subshell structures are in good agreement with the experimental magic numbers obtained in time-of-flight mass spectra of threshold photoionization, and Martin's theoretical proposition of progressive formation of atomic umbrellas. Clusters with size from 147 to 561 atoms are energetically investigated via one-by-one atomic evolution and their magic numbers are theoretically proved.