Marechal Matthieu, Dijkstra Marjolein
Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 5, CC Utrecht, The Netherlands.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 1):061405. doi: 10.1103/PhysRevE.77.061405. Epub 2008 Jun 13.
We study the stability of orientationally disordered crystal phases in a suspension of colloidal hard dumbbells using Monte Carlo simulations. For dumbbell bond length L/sigma<0.4 with L the separation of the two spheres of the dumbbell and sigma the diameter of the spheres, we determine the difference in Helmholtz free energy of a plastic crystal with a hexagonal-close-packed (hcp) and a face-centered-cubic (fcc) structure using thermodynamic integration and the lattice-switch Monte Carlo method. We find that the plastic crystal with the hcp structure is more stable than the one with the fcc structure for a large part of the stable plastic crystal regime. In addition, we study the stability of an orientationally disordered aperiodic crystal structure in which the spheres of the dumbbells are on a random-hexagonal-close-packed lattice, and the dumbbells are formed by taking random pairs of neighboring spheres. Using free-energy calculations, we determine the fluid-aperiodic crystal and periodic-aperiodic crystal coexistence regions for L/sigma>0.88 .
我们使用蒙特卡罗模拟研究了胶体硬哑铃悬浮液中取向无序晶体相的稳定性。对于哑铃键长(L/\sigma<0.4)（其中(L)是哑铃两个球体之间的间距，(\sigma)是球体的直径），我们使用热力学积分和晶格切换蒙特卡罗方法确定了具有六方密堆积（hcp）和面心立方（fcc）结构的塑性晶体的亥姆霍兹自由能差。我们发现，在大部分稳定的塑性晶体区域中，具有hcp结构的塑性晶体比具有fcc结构的塑性晶体更稳定。此外，我们研究了一种取向无序的非周期性晶体结构的稳定性，其中哑铃的球体位于随机六方密堆积晶格上，哑铃由相邻球体的随机对形成。通过自由能计算，我们确定了(L/\sigma>0.88)时流体 - 非周期性晶体和周期性 - 非周期性晶体的共存区域。
