分子动力学模拟狭缝炭孔内的毛细相变现象

Molecular Dynamics Studies of Capillary Phase-transition in the Slit Carbon Pores

采用约束恒温NVT系综分子动力学方法模拟了乙烯在不同孔径狭缝炭孔内的相变现象,并通过临界指数率和中线定律外推了相应的相变临界点。乙烯分子间的相互作用采用Le-nnard-Jones模型,乙烯分子与炭孔墙的相互作用则采用10-4-3模型。研究发现,狭缝炭孔内发生相变的真正原因是吸附内层局部密度的突变。由于狭缝炭孔墙的作用,孔内相变与体相中的汽液相变有很大差异,进而导致孔内相变的临界点与体相中汽液相变临界点有很大差异,且孔径越小,差异越大。

The constanttemperature molecular dynamics with constraint in a canonical (NVT) ensemble was used to study the capillary phasetransition of the LennardJones ethylene molecule confined in the different width slit carbon pores. The relevant critical points of capillary phasetransition were extrapolated by the law of critical power and the rectilinear diameter. It was found that the true reason caused the capillary phasetransition was the transformation of the inner adsorption layers in the slit carbon pores. Due to the carbon walls' effects, great differences exist between the capillary phasetransition in the pores and the gasliquid transition in the bulk phase of ethylene, which lead to the differences of the relevant critical properties. These differences depend strongly on the pores' sizes: the narrower the pores' sizes were, the greater differences would be.