Understanding the growth mechanism of L-cystine crystal using three dimentional Monte-Carlo simulation_ Zulaikha Alharthi
Description
These are the supplementary videos of Zulaikha's thesis entitled: understanding the growth mechanism of L-cystine crystals vis three-dimensional Monte-Carlo simulation. The objective of these materials is to give more insight into the details of the growth mechanism of L-cystine crystals using insitu AFM microscopy and CrystalGrower package. This study investigated the mechanism by which L-cystine imposter (L-cystine dimethyl ester, L-cystine methyl ester and N-acetyl L-cysteine) inhibit the crystal grwoth. The changes in crystal morphology, as well as polymorph, was interpreted using kinetic Monte-Carlo simulation. The changes in the crystal habit from hexagonal disc to hexagon prism is proved by poisoning certain sites in ab plane where the ring-like conformation of H-bonding was disrupted. The changes on the crystal surface were investigated using AFM. The study deciphers the influence of stress around the dislocation core in both growth and dissolution processes. The growth of L-cystine was followed using insitu AFM. The presence of two different types of dislocations on the surface and their importance on the growth, the different types of stress and the details of dissolution spirals are examples of the results obtained via AFM. These results are explained using CrystalGrower and extended to kinetic perspectives using simulation output. Like molecular crystals, L-cystine is characterised by anisotropic bonding that shows a couple of interesting features on the crystal surface. These were detailed using AFM. These are finger-like structures, islands amidst growing layers, composite spirals, multi-spirals and a sequence of steps colliding and annihilating each other. The finger features were successfully simulated and explained in view of growth anisotropy in the main growth directions of the crystal.