MOLECULAR DYNAMICS SIMULATION OF METAL DROPLET SPREADING ON SOLID SURFACES

Dedicated to the memory of Prof. B.D. Summ

Computer simulation of the nanodroplet spreading makes it possible to understand some laws and mechanisms of the macroscopic spreading. Besides, specific features of the spreading at the nanoscale are of interest in view of possible applications in nanotechnology. For Lennard-Jones droplets molecular dynamics predicts the diffusive law for the 1st monolayer radius identified with the wetting perimeter radius ( is the time of the spreading). A detailed discussion on this topic is presented in [1]. The laws and mechanisms of the metal droplet spreading are much less investigated in computer experiments. It is also noteworthy that the cases of nonreactive and reactive spreading should be distinguished for the metal droplet spreading. According to [2] the same diffusive law is fulfilled for the both cases of the metal droplet spreading. At the same time, our analysis of the curve presented in [3] for the Cu/Co systems gives the value 0.25 for the exponent in the power dependences ( is a constant depending on the droplet size). In [4] for Ag/Cu system the linear dependence was observed. To clarify some laws and mechanisms of the metal droplet spreading, we have simulated the metal droplet spreading on solid metal substrates using the tight-binding many-particle potential [5] and our computer program based on the isothermal molecular dynamics. For the Pb(l)/Pb(s, [100]) system we observed the law and the incomplete wetting. It is of interest that in the case of incomplete wetting the values are usually observed at the spreading of small but macroscopic droplets, of order of 1mm in diameter [6,7]. At the same time, for the Pb(l)/Ni(s, [100]) system the law and complete wetting took place. The value of equal to 0.24 also agrees with the macroscopic experimental data demonstrating that in the case of complete spreading the viscous regime of the small macroscopic droplet spreading is characterized by values 0.22 – 0.26 of the exponent n

Acknowledgements

Financial support of Ministry for Education and Science of Russian Federation is acknowledged (grant program ‘Scientific and pedagogical stuff of the innovation Russia, 2009-2013’).

References

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6. B.D. Summ, E.D. Shchukin, Colloids and Surfaces 1987, 27, 43-55.

7. B.D. Summ, V.M. Samsonov, Colloids and Surfaces 1999, 160, 63-77.