Effective surface tension for capillary fluctuations at the vapor-liquid interface

Thermal fluctuations of the surface of argon-like cluster are considered. Data obtained by molecular dynamics method are used to find effective surface tension for the capillary component of fluctuations, which characterizes the deviation of Fourier spectrum observed in numerical experiment from the spectrum of macroscopic capillary waves. The variational method was used to solve the problem. It is revealed that effective surface tension is close to constant value within a rather wide wavelength range. At the boundary of this range in the region of large wave numbers, the obtained value quickly tends to infinity, while spectral amplitudes decay thus corresponding to the theory proposed previously. The width of damping region is estimated for different temperatures and cluster sizes.