• Ke-Wei Xu

      Articles written in Pramana – Journal of Physics

    • Surface segregation of the metal impurity to the (100) surface of fcc metals

      Jian-Min Zhang Bo Wang Ke-Wei Xu

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      The surface segregation energies for a single metal impurity to the (100) surface of nine fcc metals (Cu, Ag, Au, Ni, Pd, Pt, Rh, Al and Ir) have been calculated using the MAEAM and molecular dynamics (MD) simulation. The results show that the effect of the surface is down to the fourth-layer and an oscillatory or monotonic damping $(|E_{1}| > |E_{2}| > |E_{3}| > |E_{4}|)$ phenomenon in segregation energy has been obtained. The absolute value of the segregation energy $E_{1}$ for a single impurity in the first atomic layer is much higher than that in the nether layers. Thus, whether the surface segregation will work or not is mainly determined by $E_{1}$ which is in good relation to the differences in surface energy between the impurity and host crystals $\Delta Q = Q_{\text{imp}} - Q_{\text{hos}}$. So we conclude that an impurity with lower surface energy will segregate to the surface of the host with higher surface energy.

    • Self-interstitial configuration in molybdenum studied by modified analytical embedded atom method

      Jian-Min Zhang Zhang Fang Wang Ke-Wei Xu

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      The stability of various atomic configurations containing a self-interstitial atom (SIA) in a model representing Mo has been investigated using the modified analytical embedded atom method (MAEAM). The lattice relaxations are treated with the molecular dynamics (MD) simulation at absolute zero of temperature. Six relatively stable self-interstitial configurations and formation energies have been described and calculated. The results indicate that the [1 1 1] dumbbell interstitial S111 has the lowest formation energy, and in ascending order, the sequence of the configurations is predicted to be S111, C, S110, T, S001 and O. From relaxed displacement field up to the fifth-NN atoms of six configurations, we know that the relaxed displacements depend not only on separation distances of the NN atoms from the defect centre but also strongly on the direction of the connected line between the NN atoms and the defect centre. The equilibrium distances between two nearest atoms in the core of the S111, C, S110, T, S001 and O configurations are $0.72a, 0.72a, 0.71a, 0.72a, 0.70a$ and $0.70a$, respectively.

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