Geometrical prediction of cleavage planes in crystal structures

Abstract

Cleavage is the ability of single crystals to split easily along specifically oriented planes. This phenomenon is of great interest for materials' scientists. Acquiring the data regarding cleavage is essential for the understanding of brittle fracture, plasticity and strength, as well as for the prevention of catastrophic device failures. Unfortunately, theoretical calculations of cleavage energy are demanding and often unsuitable for high-throughput searches of cleavage planes in arbitrary crystal structures. A simplified geometrical approach (GALOCS = gaps locations in crystal structures) is suggested for predicting the most promising cleavage planes. GALOCS enumerates all the possible reticular lattice planes and calculates the plane-average electron density as a function of the position of the planes in the unit cell. The assessment of the cleavage ability of the planes is based on the width and depth of planar gaps in crystal structures, which appear when observing the planes lengthwise. The method is demonstrated on two-dimensional graphene and three-dimensional silicon, quartz and LiNbO3 structures. A summary of planar gaps in a few more inorganic crystal structures is also presented.

Liquid‐Phase Exfoliation of Nonlayered Non‐Van‐Der‐Waals Crystals into Nanoplatelets

“…In crystalline materials, cleavage is defined as a fracture along a definite plane in the lattice structure, which results in an atomically smooth surface. [ 139 ] It is quantified by the cleavage energy which is closely related to the surface energy. [ 140 ] In layered materials, cleavage parallel to the atomic layers is the most favorable due to the low energy required to break the weak interlayer forces.…”

Surface Studies of β-1,3,5,7-Tetranitro-1,3,5,7-Tetrazoctane and Pentaerythritol Tetranitrate from Density Functional Tight-Binding Calculations and Implications on Crystal Shape

“…However, this may not always be the case, especially if the droplet is evaporating or reacting with the surface. 8 Moreover, it is not always easy experimentally to cleave any crystal plane of interest, 9 and therefore, finding the surface energies of planes with kinks (the so-called "K" type planes) via experiments may be difficult.…”