Formation of orientational glass and double glass in mixtures of anisotropic particles


Kyohei Takae (Kyoto University)


We propose a microscopic model of molecular dynamics simulations to study glassy dynamics of mixtures of anisotropic particles and isotropic impurities. When the sizes of host anisotropic particles and impurities are almost the same, we realize plastic crystals without orientational order in a rotator phase at relatively high temperatures. As the temperature is lowered, the disordered matrix is gradually replaced by orientationally ordered domains. Two-phase coexistence is realized in a temperature window. The impurities serve to anchor the orientations of the surrounding anisotropic particles, resulting in finely divided domains or medium range orientational order, yielding an orientational glass. We examine the rotational dynamics of the molecular orientations which is slowed down at low temperature. As the noticeable mechanical responses to applied stress, we predict the shape memory effect under a stretching cycle due to inter-variant transformation. We also argue double glass behaviour with large size differences, where both the translational and rotational disorder proliferates as increasing the concentration of the impurities.

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