arXiv subjects

Kyohei Takae

Publications and source records attributed to Kyohei Takae.

21 records · Page 2Linked to original sources

arXiv2012

Structural phase transition and orientation-strain glass formation in anisotropic particle systems with impurities in two dimensions

Using a modified Lennard-Jones model for elliptic particles and spherical impurities, we present results of molecular dynamics simulation in two dimensions. In one-component systems of elliptic particles, we find an orientation phase transition on a hexagonal lattice as the temperature $T$ is lowered. It is also a structural one because of spontaneous strain. At low $T$, there arise three martensitic variants due to the underlying lattice, leading to a shape memory effect without dislocation formation. Thermal hysteresis, a minimum of the shear modulus, and a maximum of the specific heat are also found with varying $T$. With increasing the composition $c$ of impurities, the three kinds of orientation domains are finely divided, yielding orientation-strain glass with mesoscopically ordered regions still surviving. If the impurities are large and repulsive, planar anchoring of the elliptic particles occurs around the impurity surfaces. If they are small and attractive, homeotropic anchoring occurs. Clustering of impurities is conspicuous. With increasing the anchoring power and/or the composition of the impurities, positional disorder can also be enhanced. We also investigate the rotational dynamics of the molecular orientations.

cond-mat.soft↗

arXiv2011

Structural phase transition of anisotropic particles and formation of orientation-strain glass with addition of impurities

Using a modified Lennard-Jones model for anisotropic particles, we present results of molecular dynamics simulation in two dimensions. In one-component systems, we find crystallization, a Berezinskii-Kosterlitz-Thouless phase, and a structural phase transition, as the temperatures is lowered. In the lowest temperature range, the crystal is composed of three martensitic variants on a hexagonal lattice, exhibiting the shape memory effect. With addition of larger spherical particles (impurities), these domains are finely divided, yielding glass with slow time evolution. With increasing the impurity size, the structural or translational disorder is also proliferated.

cond-mat.soft↗

arXiv2010

Phase field model of solid-liquid and liquid-liquid phase transitions in flow and elastic fields in one-component systems

We construct a phase field model including hydrodynamics and elasticity in one-component systems. It can be used to investigate solid-liquid and liquid-liquid phase transitions. Upon first-order phase transition, a velocity field is induced around interfaces in the presence of a density difference between the two phases even without applied shear flow. As applications, we present simulation results on two cases of melting, where a solid domain is placed on a heated wall in one case and is suspended in a warmer liquid under shear flow in the other. We find that the solid domain moves or rotates as a whole due to elasticity, releasing latent heat. We also examine the liquid-liquid phase transition of a highly viscous domain into a less viscous liquid on a heated wall, where an inhomogeneous velocity field is induced within a projected part of the domain. In these phase transitions, the interface temperature is nearly equal to the coexisting temperature $T_{\rm cx}(p)$ away from the heated wall in the presence of heat flow in the surrounding liquid.

cond-mat.soft↗