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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

As interfaces play a more important role in high-volume-fraction ceramic/metal composites because of containing more hetero-phase interfaces, it is a great challenge to control the interfaces in such composites to balance their strength and plasticity and to obtain high performances. In this work, 50–60 vol% (TiC + TiB2)/Al composites were fabricated in Al–Ti–B4C system via a one-step method of reaction and densification, and their interface bonding and mechanical properties were compared with those of in-situ TiC/Al composites. Apparently, the defects, such as interfacial discontinuity, macro-pores, coarsening and agglomeration of particles, caused by increased ceramic content in the TiC/Al composites, are eliminated in the (TiC + TiB2)/Al composites using Al–Ti–B4C system. The 60 vol% (TiC + TiB2)/Al composite exhibits significantly enhanced mechanical properties, i.e. 70.5%, 60.7% and 69.8% respectively higher yield strength, ultimate compressive strength and plastic strain than 60 vol% TiC/Al composite. Such enhanced mechanical properties are attributed to the improvement in interface bonding strength and therefore the increase in the energy dissipation of crack propagation. The formation of enhanced interface in the (TiC + TiB2)/Al composites results from the reduction in the reaction heat in the Al–Ti–B4C system, improved crystallographic match and improved adhesion work between ceramic particles and matrix. This work may provide a new idea for the design and control of interfaces in high-volume-fraction ceramic-metal composites.

Interface formation and bonding control in high-volume-fraction (TiC+TiB2)/Al composites and their roles in enhancing properties

Electroless copper deposition: A critical review

Understanding grain refining and anti Si-poisoning effect in Al-10Si/Al-5Nb-B system

Stability of the Al/TiB 2 interface and doping effects of Mg/Si

Microstructure evolution of 15 wt% boron carbide particle reinforced aluminum matrix composites (B4C/Al composites) with titanium addition during liquid-stirring process was dynamically characteriz...

Microstructure evolution of 15 wt% boron carbide/aluminum composites during liquid-stirring process:

The crystal–melt interfacial free energy is an important quantity governing many kinetic phenomena including solidification and crystal growth. Although general calculation methods are available, it is still difficult to obtain the interfacial energies that differ only slightly due to anisotropy. Here, we report such a calculation of Al crystal–melt interfacial energy based on the general framework of the capillary fluctuation method (CFM). The subtle dependence of both the melting temperature and interfacial free energy at melting temperature on the crystal interface orientation was examined. For Al, the average melting temperature is obtained at 934.79 ± 5 K and the orientationally averaged mean interfacial free energy is 98.35 mJ/m2. In addition, the anisotropy of the interfacial free energy is found weak, nevertheless with the values ranked as γ100 > γ110 > γ111.

Qiulin Li

Papers

Stability of the Al/TiB 2 interface and doping effects of Mg/Si

Microstructure evolution of 15 wt% boron carbide/aluminum composites during liquid-stirring process:

Anisotropic crystal–melt interfacial energy and stiffness of aluminum

The effect of dislocations on irradiation-induced vacancy-like defects in FeCu alloy and reactor pressure vessel steel

The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys