**Universal fast mode regime in wetting kinetics**

SSH Zaidi and PK Jaiswal and M Priya and S Puri, PHYSICAL REVIEW E, 106, L052801 (2022).

DOI: 10.1103/PhysRevE.106.L052801

We present simulation results from a comprehensive molecular dynamics (MD) study of surface-directed spinodal decomposition (SDSD) in unstable symmetric binary mixtures at wetting surfaces. We consider long -ranged and short-ranged surface fields to investigate the early stage wetting kinetics. The attractive part of the long-ranged potential is of the form V (z) -z-n, where z is the distance from the surface and n is the power-law exponent. We find that the wetting-layer thickness R1(t) at very early times exhibits a power-law growth with an exponent alpha = 1/(n + 2). It then crosses over to a universal fast-mode regime with alpha = 3/2. In contrast, for the short-ranged surface potential, a logarithmic behavior in R1(t) is observed at initial times. Remarkably, similar rapid growth is seen in this case too. We provide phenomenological arguments to understand these growth laws. Our MD results firmly establish the existence of universal fast-mode kinetics and settle the related controversy.

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