Abstract
The Poisson's ratio of the fcc hard-core repulsive Yukawa crystals with size polydispersity was determined by Monte Carlo simulations in the isothermal-isobaric ensemble. The effect of size polydispersity on the auxetic properties of Yukawa crystals has been studied. It has been found that an increase of particle size polydispersity causes a decrease of the Poisson's ratio in auxetic directions as well as appearance of a negative Poisson's ratio in formerly non-auxetic directions. A measure of auxeticity was introduced to estimate quantitatively an enhancement of auxetic properties in polydisperse Yukawa crystals. The proposed measure of auxeticity can be applied to appraise the auxeticity of any studied system.
Highlights
Interest in colloidal crystals[1] comes from their potential applications in optoelectronics,[2] photonics,[3] and medicine.[4]
In order to obtain materials with desired physical properties, studies are made on colloids composed of both spherically symmetric and more complex molecules like dumbbells[5,6] and further on mixtures of spherical and cylindrical molecules.[7]
Spherical particles with hardcore repulsive Yukawa interaction form body-centered-cubic or face-centred-cubic crystals depending on the Debye screening length and the volume fraction, which have been observed in experiments[14] and computer simulations.[15,16]
Summary
Interest in colloidal crystals[1] comes from their potential applications in optoelectronics,[2] photonics,[3] and medicine.[4] In order to obtain materials with desired physical properties, studies are made on colloids composed of both spherically symmetric and more complex molecules like dumbbells[5,6] and further on mixtures of spherical and cylindrical molecules.[7] Electric or magnetic fields are used to control the selfassembly of colloidal crystals,[8,9] as well as to obtain desired structures[10,11] through the changes of molecular orientation. The electric field can impact the optical properties of colloids composed from spherically symmetric particles.[12] In the case of spherical particles, a large difference in the elastic properties of face-centered-cubic (fcc) and hexagonal-closepacked hard-sphere crystals was found.[13] The latter model molecule (hard sphere) is important for colloids and is the limiting case of Yukawa particles. In these crystals a negative Poisson’s ratio in one of the main crystallographic directions is observed
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