Molecular dynamics simulations of crystallization under confinement at triple point conditions

摘要

Molecular dynamics computer simulations of crystallization of a Lennard-Jones system under confinement conditions in the vincinity of the triple point are reported. We calculate the force exerted on a crystal by a melt when it crytallizes. The force due to crystallization is reflected in the disjoining pressure isotherms as a characteristic peak. We find that at conditions of high confinement, i.e., pore thicknesses of approx = 1 nm, the disjoining pressure can rise up to approx 10~8 Pa. We also analyze the dependence of the crytallization under confinement as a function of temperature. Confinement can stabilize the crystal phase at temperatures significantly higher than the melting temperature. For the systems studied in the work, a pore of 1 nm thickness stabilizes the crystal phase at temperatures up to 45 higher than the normal melting temperature. In addition we consider the disjoining pressure profile along confining pore lits of finite lengths. The finite size effects due to the pore length modifies the value of the force close to the pore edge. There exist a reduction of the total disjoining pressure in short pores with respect to long pores. The simulations show that these effects are more noticeable for pore lengths below 3 nm.