Auxetic Properties of a f.c.c. Crystal of Hard Spheres with an Array of [001]-Nanochannels Filled by Hard Spheres of Another Diameter (Phys. Status Solidi B 1/2019)

Simple structural modifications can essentially affect the auxetic properties of materials, see article no. 1800611 by Jakub W. Narojczyk et al. The Poisson's ratio (PR) of a f.c.c. crystal of unit-diameter hard spheres (green in the cover image) with a periodic array of nanochannels filled by hard spheres of another diameter (red) has been studied at high pressure. The resulting nanocomposite shows tetragonal symmetry. When the ‘inclusion’ spheres are by 9% greater than the ‘matrix’ spheres, the minimum value of PR, ≈–0.87, is significantly lower than its value, ≈–0.06, obtained for identical spheres. The blue surfaces illustrate (in spherical coordinates) the most negative PR value in various directions of the applied external stress, for the cubic crystal (left) and tetragonal crystal (right), respectively.