Molecular Dynamics Simulation of Bubble Nucleation in Superheated Liquid

The bubble homogeneous nucleation in superheated liquid argon is studied by molecular dynamics simulation in NVT ensemble. L-J potential is adopted for the interaction of argon atom. The simulated particle numbers of argon atom is 10976. The non-dimensional size of simulated box is 27.8×27.8×27.8. The initial non-dimensional temperature and density are 0.4 and 0.51 separately. The results show that the bubble homogeneous nucleation is divided into the waiting process, the appearing process of numerous small bubble nucleuses and the aggregation process of small bubble nucleuses. By fitting simulated data, we find that the bubble nucleation rate is eight orders of magnitudes bigger than the result of classic nucleation theory. The bubble nucleation rate increases along with the increasing of density and superheated temperature, which agrees well with one of classic nucleation theory.

Silicide Formation for Ni and Pd Bilayers on Si(100) Substrates

ABSTRACTThe silicide formation for Ni/Pd and Pd/Ni bilayers on Si(100) substrates was investigated. X-ray diffraction and photoelectron spectroscopy (XPS) depth profiling have been applied to study the phase formation of the silicide. We found that with addition of Pd into Ni/Si, a uniform layer of ternary Ni1−xPdxSi layer formed and kept stable for a wide temperature range. The lattice parameter of Ni1−xPdxSi as a function of Pd addition was calculated. The nucleation temperature of NiSi2 was delayed due to the addition of Pd. The higher the Pd addition, the larger the increase in NiSi2 nucleation temperature. We also studied the effect on the addition of Ni to the Pd/Si reaction. For pure Pd/Si reaction PdSi nucleated from Pd2Si at 750°C or above. For Ni/Pd/Si reaction, Pd2Si changed to Ni1−xPdxSi at temperature lower than 750°C due to the incorporation of Ni. The phenomena were explained by classic nucleation theory taking into account the effect of mixing entropy effect.