Chemistry

Chemists challenge traditional views on crystal growth

Graphical summary. Credit: Matter (2024). DOI: 10.1016/j.matt.2024.08.011

Remember the old high school chemistry experiment where salt crystals precipitate from a salt solution, or rock candy crystals form from sugar water? Learn about how crystals form in these solutions It turns out that your understanding of may be wrong.

A new theory elucidates the crystallization process and shows that the substance that crystallizes is the main component in the solution, i.e. the solvent rather than the solute. The theory could impact everything from drug development to understanding climate change.

The paper will be published in the magazine Matter.

“Crystals are everywhere, and we use them in everything from technology to medicine,” said James Martin, a professor of chemistry at North Carolina State University and author of a paper in Matter that outlines crystals. “However, there is a lack of actual understanding of the crystallization process.” theory.

“The common idea about dissolution and precipitation is that they are essentially the opposite of each other, but that’s actually not the case. In fact, they are completely different processes,” Martin says.

“As an example, we’ll use a high school chemistry experiment where you take a precipitate out of a solution. When you dissolve a salt (the solute) in water (the solvent), the water becomes dominant. By basically tearing the salt apart, The water dissolves the salt,” Martin said. Say. “If you want to grow salt crystals from that solution, the dominant phase has to be the salt. The salt is the solvent at that point, and it’s what forms the crystals.”

Thermodynamic phase diagrams that describe concentration- and temperature-dependent transition points in solutions can be used to explain a new theory called transition region theory.

This theory states that crystallization occurs in two stages. First, a melt-like pre-growth intermediate is formed. The intermediates are then organized into crystalline structures.

“To grow crystals from solution, you need to quickly separate the solvent and solute,” Martin says. “When we say ‘melt’ here, we are referring to the pure phase of the solvent before crystal formation. The difference here is that my theory shows that you get better and faster crystal growth by moving the solution towards the next condition. In other words, the solvent, not the impurities in the solvent, controls the rate of crystal growth. ”

Martin applied his theory to various solution, concentration, and temperature conditions and found that it accurately described the rate and size of crystal formation.

“The main problem with previous explanations of crystallization was the recognition that crystals grow by the diffusion and attachment of independent solute particles to growing crystal interfaces,” Martin says. “Instead, we need to understand the cooperative ensemble of solvents to explain crystal growth.”

Martin said a key aspect of the new theory is its focus on understanding how solute impurities disrupt cooperative ensembles of solvents.

“By understanding the interaction between temperature and concentration, we can accurately predict how fast and large crystals will grow from solution.”

Martin believes this phase diagram could have important applications not only in crystal formation, but also in preventing crystal formation, such as preventing the growth of kidney stones.

“Crystals power technology. They are all around us and impact our daily lives,” Martin says. “This theory provides researchers with an easy tool to understand the ‘magic’ of crystal growth and make better predictions. It is a fundamental science that will help solve all kinds of real-world problems. This is an example of how to lay the foundation for

Further information: James D. Martin, Solutes don’t crystallize! Insights from phase diagrams reveal the “magic” of crystallization, Matter (2024). DOI: 10.1016/j.matt.2024.08.011

Provided by North Carolina State University

Citation: Chemist challenges traditional views on crystal growth (October 2, 2024) from https://phys.org/news/2024-10-chemist-traditional-views-crystal-growth.html Retrieved October 3, 2024

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