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arXiv 1710.02478cond-mat.soft
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狭缝状细孔中弱各向异性硬杆的有序转变

Ordering transitions of weakly anisotropic hard rods in narrow slit-like pores

Roohollah Aliabadi, Peter Gurin, Enrique Velasco, Szabolcs Varga

摘要:

利用第二维里密度泛函理论的Parsons-Lee修正,研究了长L、直径D(L>D)的硬矩形棒系统中强约束对位置和取向有序的影响.所述棒是非介晶的(L/D<3)并且被限制在两个平行的硬壁之间,其中孔的宽度(H)以这样的方式选择,使得平面(颗粒的长轴平行于壁)和垂面(颗粒的长轴垂直于壁)排序都是可能的,并且允许在孔中形成最多两个层。在的极限限制下,只有一个层结构出现,我们观察到从平面到垂直流体层的结构转变,密度增加,这变得更加尖锐的L->H。在较宽的孔(2D<H<3D)中,具有两层的平面有序、垂面有序、甚至组合的双层结构(一层是垂面的,而另一层是平面的)可以在高密度下稳定。此外,在不同结构之间可以看到一阶相变。其中之一出现在单层和双层之间,平面订单在相对较低的包装分数。

英文摘要:

The effect of strong confinement on the positional and orientational ordering is examined in a system of hard rectangular rods with length L and diameter D (L>D) using the Parsons-Lee modification of the second virial density functional theory. The rods are nonmesogenic (L/D<3)and confined between two parallel hard walls, where the width of the pore (H) is chosen in such a way that both planar (particle's long axis parallel to the walls) and homeotropic (particle's long axis perpendicular to the walls) orderings are possible and a maximum of two layers are allowed to form in the pore. In the extreme confinement limit of ,where only one layer structures appear, we observe a structural transition from a planar to a homeotropic fluid layer with increasing density, which becomes sharper as L->H. In wider pores (2D<H<3D) planar order with two layers, homeotropic order, and even combined bilayer structures (one layer is homeotropic, while the other is planar) can be stabilized at high densities. Moreover, first order phase transitions can be seen between different structures. One of them emerges between a monolayer and a bilayer with planar orders at relatively low packing fractions.

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