Solvent and additive interactions as determinants in the nucleation pathway: general discussion

Abstract

Sarah Price opened a general discussion of the paper by Sven Schroeder: I have been generating the thermodynamically plausible crystal structures of organic molecules for many years, and back in 2004 we did a crystal structure prediction (CSP) study on imidazole 1 and found that it was relatively straightforward. Following your paper, we have reclassied the low energy structures according to the tilt within the hydrogen-bonded chain and the relative direction of the chains. Although the observed structure was the global minimum, two other structures with a displacement of otherwise identical layers are very close in energy. Do you think that if imidazole had crystallised in one of these alternative structures it would be distinguishable by NEXAFS? This would be a very sensitive test of whether NEXAFS combined with CSP could be used in characterising crystal structures. 1. S. L. Price, B, Patel, P. Pridhanani-Jethani and A. Torrisi, Crystal structure prediction and polymorphism -some mutual insights, Transactions of the American Crystallography Association, 2004, 39, 1-12.Sven Schroeder replied: We are working towards this aim. We have so far established that NEXAFS is extremely sensitive to variations in speciation in † Electronic Supplementary Information available: copies of the slides presented at the meeting by Wenhao Sun on the subject of metastable aragonite CaCO 3 nucleation in seawater. This journal is

Induction time of a polymorphic transformation

“…Regardless of the physical mechanism, the lower surface energy of metastable phases explains the initial precipitation of metastable polymorphs during crystallization. Manipulating solution chemistry can also promote the formation of a metastable phase, as solvent or solution additives may selectively influence the surface energies of competing polymorphs, [28][29][30][31][32] which could manifest in orders of magnitude changes in their relative nucleation rates.…”

Three Reasons Why Aspartic Acid and Glutamic Acid Sequences Have a Surprisingly Different Influence on Mineralization

“…Analyzing how additives affect mineralization processes in biological or artificial systems, however, is a challenging task, because influences can occur in various stages of the mineralization process. This involves interactions with crystal surfaces on a millimeter scale but also interactions with tiny nuclei or crystal precursors on an Ångström scale. − Especially getting atomic/molecular insights into the early stages of mineralization is difficult through experimentation, though the multiple roles that additives can play in influencing mineralization processes have become more and more apparent. − Molecular dynamics simulation turned out to be a valuable tool to elucidate this gap. − …”

Crystal Structures and Phase Behavior of Sulfadiazine and a Method for the Preparation of Aggregates with Good Performance

“…The solubility of the powder in the NMP solvent was much higher than that in water, by four orders of magnitude. This means that the solute‐solvent interaction is stronger in the NMP solvent . The amino hydrogen of the SD molecule formed N–H···O interactions with the carbonyl groups of the NMP solvent molecule.…”