How Cavities Affect Chemical Reactions - Unveiling the Mystery of Slowed Chemical Reactions
Category Physics Saturday - May 13 2023, 00:03 UTC - 1 year ago An international research team has revealed the underlying mechanism of why chemical reactions are slowed down in mirrored cavities, where molecules interact with light. Using Quantum-Electrodynamical Density-Functional Theory, the team found that the conditions inside the optical cavity affect the energy which makes atoms vibrate around the molecule’s single bonds, which is critical for the reaction.
Scientists have discovered why chemical reactions are slowed down in mirrored cavities, where molecules interact with light.
The team used Quantum-Electrodynamical Density-Functional Theory to find that the conditions inside the optical cavity affected the energy that makes atoms vibrate around the molecule’s single bonds, which are critical to the reaction.
Chemical processes are all around us. From novel materials to more effective medicines or plastic products – chemical reactions play a key role in the design of the things we use every day. Scientists constantly search for better ways to control these reactions, for example, to develop new materials. Now an international research team led by the MPSD has found an explanation why chemical reactions are slowed down inside mirrored cavities, where molecules are forced to interact with light. Their work, now published in the journal Nature Communications, is a key step in understanding this experimentally observed process.
Chemical reactions occur on the scale of atomic vibrations — one million times smaller than the thickness of a human hair. These tiny movements are difficult to control. Established methods include the control of temperature or providing surfaces and complexes in solution made from rare materials. They tackle the problem on a larger scale and cannot target specific parts of the molecule. Ideally, researchers would like to provide only a small amount of energy to some atoms at the right time, just like a billiard player wants to nudge just one ball on the table.
In recent years, it became clear that molecules undergo fundamental changes when they are placed in optical cavities with opposing mirrors. Inside those confines, the system is forced to interact with virtual light, or photons. Crucially, this interaction changes the rate of chemical reactions – an effect that was observed in experiments but whose underlying mechanism remained a mystery.
Now a team of theoretical physicists from Germany, Sweden, Italy, and the USA has come up with a possible explanation that qualitatively agrees with the experimental results. The team involved researchers from the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) in Hamburg, Germany, Chalmers University of Technology in Sweden, the Center for Computational Quantum Physics at the Flatiron Institute, Harvard University (both in the U.S.A.), and the Istituto per i Processi Chimico Fisici at the CNR (National Research Council) in Italy.
Using an advanced theoretical method, called Quantum-Electrodynamical Density-Functional Theory (QEDFT), the authors have unveiled the microscopic mechanism which reduces the chemical reaction rate, for the specific case of the deprotection reaction of 1-phenyl-2-trimethylsilylacetylene. Their findings are in agreement with the observations by the group of Thomas Ebbesen in Strasbourg.
The team discovered that the conditions inside the optical cavity affect the energy which makes the atoms vibrate around the molecule’s single bonds, which are critical for the chemical reaction. Outside the cavity, that energy is usually deposited in a single bond during the reaction, which can ultimately break the bond – a key step in a chemical reaction. "However, we find that the cavity introduces a new pathway, so tthe energy which is deposited in the bond is actually removed from it again before the bond can be broken,” explains lead author Yohai Rozenberg, collaborator of the MPSD and now professor at Columbia University. “This in turn necessarily reduces the rate of the reaction.” .
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