Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Aluminum graphene nanoflakes composite depicts many useful properties such as excellent mechanical strength, lightweight, high electrical, thermal properties, etc. Aggregation and dispersion of gra...

Reactivity-Controlled Aggregation of Graphene Nanoflakes in Aluminum Matrix: Atomistic Molecular Dynamics Simulation

Aluminum graphene nanoflakes composite depicts many useful properties such as excellent mechanical strength, lightweight, high electrical, thermal properties, etc. Aggregation and dispersion of graphene nanoflakes in aluminum matrix highly influence the above-mentioned properties. In this paper, aggregation of graphene nanoflakes in aluminum matrix has been studied using molecular dynamics simulation. During simulations, adaptive intermolecular reactive empirical bond order (AIREBO) and embedded atom method force field were used for graphene nanoflakes and aluminum, respectively. AIREBO potential is capable of reproducing sp²–sp² (covalent) bond formation or breaking between the reactive edge of graphene nanoflakes. The reactive edges of graphene nanoflakes form covalent bond with the neighboring graphene that produces a unique interconnected network in aluminum matrix. However, reactivity of graphene edge exclusively depends on the interfacial interaction between graphene and aluminum. Further, interfacial interactions significantly influence the crystallization temperature of aluminum. The adaptive common neighbor analysis, radial distribution function, mean square displacement, solvent-accessible surface area, and potential energy evolution have been used to characterize the properties of aluminum graphene nanoflakes composite. The results of this study may provide a comprehensive understanding of the interfacial properties of graphene aluminum nanocomposites, which help to improve the performance of nanocomposites materials.

Ultra–low loss tangent and giant dielectric permittivity with excellent temperature stability of TiO2 co-doped with isovalent-Zr4+/pentavalent-Ta5+ ions

The dielectric constant (e’), dielectric loss tangent (tan δ), and non-Ohmic properties of Sm3+-doped CaCu3Ti4.2O12, i.e., Ca1-1.5xSmxCu3Ti4.2O12 (x = 0.05 and 0.10) ceramics sintered at 1080 °C and 1100 °C were studied. Interestingly, a giant- e’ (∼9602–16169) with very low tan δ values (∼0.021–0.039) was attained in ceramics sintered at 1100 °C. Moreover, compared to undoped CaCu3Ti4.2O12 ceramics sintered at 1100 °C in our previous work, the tan δ values of Sm3+–doped CaCu3Ti4.2O12 ceramics (x = 0.05 and 0.10) sintered at 1100 °C were found to significantly decrease by 3.06% and 5.68%, respectively. Additionally, these ceramics exhibited non-Ohmic behavior with higher nonlinear coefficient (α)values of ∼ 8.7–22.1. It can be suggested that these very low tan δ values are associated with high grain boundary resistances (Rgb), as is confirmed by the impedance complex plane plot (Z* plot) for this material. Effects of Sm3+ doping and sintering temperature on CaCu3Ti4.2O12 ceramics played a significant role in increasing Rgb values as well as enhancing the nonlinear J-E relationship and dielectric properties of this material. FESEM and elemental mapping with EDXS spectra, as well as XRD techniques, were employed to elucidate the microstructural and structural nature of all ceramics. Moreover, XPS was performed to reveal the Cu+:Cu2+:Cu3+ ratios of these ceramics. The results indicated a semiconducting behavior of the grains. Additionally, it was found that the decreased e’ values were correlated with lower Cu+:Cu2+ ratios and concurrently increasing levels of Sm3+ dopant.

Effect of sintering temperature and Sm 3+ doping on the dielectric properties and non-Ohmic behavior of Ca 1-1.5 x Sm x Cu 3 Ti 4.2 O 12 (x = 0.05 and 0.10) ceramics

The abnormal multiple dielectric relaxation responses of Al3+ and Nb5+ co-doped rutile TiO2 ceramics

In the study of college physics, experiment is the source of students' discovery and exploration of problems, which plays a crucial role in college physics and is also the focus of physics teaching...

Design and implementation of college physics teaching platform based on virtual experiment scene

Mechanical behaviour of rapidly solidified aluminium with multiple twinned nanograins: A molecular dynamics simulation study

This study investigates the magnetic dynamics of a ferroelectric/ferromagnetic heterostructure mediated by a charge/strain-induced magnetoelectric interaction that exhibits a pronounced dynamic magnetic response to an electric field. In the experimental process, the epitaxial strain gave rise to electrically tunable uniaxial magnetic anisotropy, and spin accumulation at the interface led to large anisotropic damping with a C 2 υ symmetry. The results show the significant potential for applications of composite multiferroics and provide a feasible approach for high-performance devices that rely on electrically controlled magnetism.

Xiao-Gang Zhao

Papers

The abnormal multiple dielectric relaxation responses of Al3+ and Nb5+ co-doped rutile TiO2 ceramics

Design and implementation of college physics teaching platform based on virtual experiment scene

Mechanical behaviour of rapidly solidified aluminium with multiple twinned nanograins: A molecular dynamics simulation study

Polarization-induced anisotropic damping in Co/[Pb (Mg1/3Nb2/3)O3]0.7–[PbTiO3]0.3 (011) heterostructure