Gaussian Grooves Propagating Across a Moving Curved Interface in Directional Solidification

Abstract

In gratitude to Antoine Skoulios for original and illuminating insights on complex materials, and, to celebrate the emergence of his new adventures, this article is a synopsis of astonishing observations made about a decade ago on a deceptively simple material, succinonitrile, during its crystal growth from a curved phase boundary traveling in narrow channels. For a range of pulling speeds, v, v_cl < v < v_c2, the flat interface transforms, first, to a curved one, then, to a cellular one by groove propagation. The shape of the lead groove is Gaussian, consistent with a linear concentration gradient across the interface, and the pattern has a well-defined wavelength. When v < v_c1, the interface remains flat and when v > v_c2, the pattern is time dependent.