Abstract. We present atomic-scale computer simulations in equiatomic L10-CoPt where Molecular Dynamics and Monte Carlo techniques have both been applied to study the vacancy-atom exchange and kinetics relaxation. The atomic potential is determined using a Tight-Binding formalism within the Second-Moment Approximation. It is used to evaluate the different saddle-point energies involved in a vacancy-atom exchange between nearest-neighbour sites. The potential and the saddle-point energies have been used to simulate the relaxation of the long-range order in CoPt using a Monte Carlo technique. A vacancy migration energy of 0.73 ± 0.15 eV and an order-disorder transition temperature of 935 K have been found. PACS

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Abstract. Monte Carlo simulations have been performed to investigate the relaxation of the L1 0 long-range order in dimensionally reduced systems. The effect of the number of (001)-type monatomic layers and of the pair interaction energies on these kinetics has been examined. The vacancy migration energies have been deduced from the Arrhenius plots of the relaxation times. A substantial increase in the migration energy for small film thickness is observed. The results agree with previous Monte Carlo simulations and with recent experimental results in L1 0 thin films and multilayers.

We study performance and scaling of the Berlin Quantum Chromodynamics Program (BQCD) on the SGI Altix 4700 at Leibniz Supercomputing Centre (LRZ). We employ different communication methods (MPI, MPI with two OpenMP threads per process, as well as the shmem library) and run the MPI version on the two types of nodes of that machine. For comparison with other machines we made performance measurements on an IBM p690 cluster and a Cray XT4.

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