Study on adhesion loose packing limit of adhesive ellipsoids based on random ballistic deposition method

The effect of the geometric shape of ellipsoids (covering a wide aspect ratio range from 0.003 to 60) on the structure of adhesive loose packings is investigated by the random ballistic deposition method with the hit-stick-freeze assumption. Statistical results show that the packing density of spherical particles is the largest, which is 0.1469. As the particle shape deviates from spherical shape, the packing density decreases rapidly. When the aspect ratio is below 0.1 and above 10, the packing density is approximately correlated with the aspect ratio in 1 and −2 power-law relations. The local coordination number is independent of the particle shape, which not only follows the Gaussian normal distribution, but also has a common average value of 2.001. This result indicates that for packing systems of non-spherical particles controlled by short-range interparticle contact interactions, 2 is the lowest coordination number for forming a mechanically stable structure. The radial distribution function shows that the local packing structure is dominated by local minor-to-major and major-to-major contact for oblate ellipsoids, and by local minor-to-minor and minor-to-major contact for prolate ellipsoids. Finally, analogous to the classical filling theory of spherical particles, a predicting correlation between the packing density and the aspect ratio is established.