One-, Two-, and Three-Dimensional Hopping Dynamics

Abstract

Hopping dynamics in glass has been known for quite a long time. In contrast, hopping dynamics in smectic-A (SmA) and hexatic smectic-B (HexB) liquid crystals (LC) has been observed only recently. The hopping in SmA phase occurs among the smectic layers (one-dimensionally), while hopping in HexB phase occurs inside the layers (two-dimensionally). The hopping dynamics in SmA and HexB liquid crystal phases is investigated by parallel soft-core spherocylinders, while three-dimensional hopping dynamics in inherent glassy states is investigated by systems of Weeks-Chandler-Andersen (WCA) spheres. The temperature dependence of diffusion coefficients of hopping in SmA phase can be described by the Arrhenius equation characteristic of activation process. In HexB LC phase, the diffusion coefficients saturate at higher temperatures. In a system of WCA spheres, the values and temperature dependence of diffusion coefficients depend on the observed states.

Molecular Dynamics Simulations of One-, Two-, Three-dimensional Hopping Dynamics

“…The pressure is set to P = 10 4 in the simulations to observe the hopping dynamics in similar temperature range of HexB LC at P = 10 3 . Six metastable states of WCA spheres are reported in [1]. Here we report additional 10 states.…”

“…In this short paper, we report new thermodynamic metastable states of monodispersed isotropic spheres in addition to the states already reported in [1,5]. Our simulated system consists of single component (monodispersed) soft-spheres of WCA potential [6], i.e.…”

“…In contrast, hopping dynamics in liquid crystal (LC) phases has been observed recently [1]. Liquid crystals (LCs) are soft matter which flow, but have remaining order to some extent.…”

“…This stimulated investigations of hopping dynamics in other systems including thermotropic LC phases, which consists of much shorter molecules compared to viruses ( [1] and references therein). The diffusion coefficients parallel to the particles D of hopping dynamics in SmA phase were investigated by constant pressure and temperature MD simulation of soft parallel spherocylinders.…”

Entropy and Heat Capacity Calculations by Thermodynamic Approach

“…A symplectic integrator preserves the structure of the canonical Hamiltonian equation of motion. The advantage of this new method is that not only thermodynamic equilibrium phases but also metastable states can be obtained by constant pressure and temperature processes [1,11,12]. In the calculations, H 0 is taken to be the initial value of H a (t = 0).…”