Using molecular dynamics to unravel phase composition behavior of nano-size pores in frozen soils: Does Young-Laplace equation apply in low temperature range?

摘要

The phase composition curve of frozen soils is a fundamental relationship in understanding permafrost and seasonally frozen soils. However, due to the complex interplay between adsorption and capillarity, a clear physically based understanding of the phase composition curve in the low temperature range, i.e., 265 K, is still absent. Especially, it is unclear whether the Young-Laplace equation corresponding to capillarity still holds in nano-size pores where adsorption could dominate. In this paper, a framework based on molecular dynamics was developed to investigate the phase transition behavior of water confined in nano-size pores. A series of simulations was conducted to unravel the effects of the pore size and wettability on the freezing and melting of pore water. This is the first time that the phase composition behavior of frozen soils is analyzed using molecular dynamics. It is found that the Young-Laplace equation may not apply in the low temperature range.