A new generic model potential for mesogenic systems: square well line potential of variable range.
A new generic model potential for mesogenic systems: square well line potential of variable range.
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DOI：
10.1063/1.3264109
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发表时间：
2009-11
期刊：
影响因子：
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通讯作者：
S. Varga;F. Vesely
中科院分区：
文献类型：
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作者：
S. Varga;F. Vesely
推导了一个单点对势来近似线性n点平方阱相互作用。由此得到的方形井线（SWL）势是解析的，相当平滑，并再现了多位点对能量的距离和方向依赖性。除了长度s(1)和能量epsilon的单位外，它只包含三个控制参数n、L和s(2)。新模型相对于传统势（如Gay-Berne和Kihara）的优势在于，n、L和s(2)是物理上有意义的量，并且没有引入额外的可调参数。有了SWL势，即使很长的方阱链分子也可以在蒙特卡罗（MC）模拟中处理；此外，该模型很适合摄动理论。利用类onsager理论，我们测试了分子伸长率、温度和方阱电位范围对汽-液和向列-近晶相变的影响。我们发现SWL流体的气液双极性与方形井哑铃的MC结果吻合得很好。对于排斥性SWL粒子，改变相互作用范围s(2)对NS跃迁的影响与在fd病毒的实际悬浮液中离子强度的变化相似。
A single-site pair potential is derived to approximate the linear n-site square well interaction. The resulting square well line (SWL) potential is analytical, fairly smooth, and reproduces the distance and orientation dependence of the multisite pair energy. It contains only three control parameters n, L, and s(2), in addition to the units of length s(1) and energy epsilon. The advantages of the new model over the traditional potentials such as Gay-Berne and Kihara are that n, L, and s(2) are physically meaningful quantities and that no additional adjustable parameters are introduced. With the SWL potential even very long square well chain molecules may be treated in Monte Carlo (MC) simulations; moreover the model is well suited for perturbation theory. Using Onsager-like theories we test the effect of molecular elongation, temperature, and the range of the square well potential on the vapor-liquid and nematic-smectic A (NS) phase transitions. We find that the vapor-liquid binodal of the SWL fluid is in good agreement with MC results for square well dumbbells. For repulsive SWL particles, varying the interaction range s(2) results in a similar effect on the NS transition as the change in the ionic strength in a real suspension of fd viruses.