ZB 10 - Soft Condensed Matter (R. Holyst)

A molecular dynamics test of the Hertz-Knudsen equation for evaporating liquids

Author(s): Holyst, Robert and Litniewski, Marek and Jakubczyk, Daniel
Title: A molecular dynamics test of the Hertz-Knudsen equation for evaporating liquids
Abstract: The precise determination of evaporation flux from liquid surfaces gives over evaporation-driven self-assembly in soft matter systems. Hertz-Knudsen (HK) equation is commonly used to predict evaporation This equation states that the flux is proportional to the between the pressure in the system and the equilibrium for liquid/vapor coexistence. We applied molecular dynamics simulations of one component Lennard-Jones (LJ) fluid to test the equation for a wide range of thermodynamic parameters covering more one order of magnitude in the values of flux. The flux determined the simulations was 3.6 times larger than that computed from the HK However, the flux was constant over time while the pressures the HK equation exhibited strong fluctuations during simulations. observation suggests that the HK equation may not appropriately the physical mechanism of evaporation. We discuss this issue in context of momentum flux during evaporation and mechanical in this process. Most probably the process of evaporation is by a tiny difference between the liquid pressure and the gas This difference is equal to the momentum flux i.e. momentum by the molecules leaving the surface of the liquid during The average velocity in the evaporation flux is very small to three orders of magnitude smaller than the typical velocity of atoms). Therefore the distribution of velocities of LJ atoms does not from the Maxwell-Boltzmann distribution, even in the interfacial region.
Pages: 7201-7206
Journal: SOFT MATTER
Volume: 11
ID: ISI:000360656900016
Year: 2015
DOI: 10.1039/c5sm01508a