Quantum Chemistry - With quantum theory scientists also recognized a whole new connection between physics and chemistry.
How atoms combine to form molecules and other compounds is determined by the quantum properties of the electron shells in those atoms.
That implies that chemistry is nothing more than applied quantum physics.
Only with knowledge of quantum physics can the structures of chemical bonds be understood. Some readers may recall the cloud-like structures that form around the atomic nucleus.
These clouds, which are called orbitals, are nothing but approximate solutions of the fundamental equation of quantum mechanics, the Schrödinger equation.
They determine the probabilities of finding the electrons at different positions (but note that these solutions only consider the interactions between the electrons and the atomic nucleus, not those between the electrons).
“Quantum chemistry” consists in calculating the electronic structures of molecules using the theoretical and mathematical methods of quantum physics and thereby analyzing properties such as their reactive behavior, the nature and strength of their chemical bonds, and resonances or hybridizations.
The ever increasing power of computers makes it possible to determine chemical processes and compounds more and more precisely, and this has gained great significance not only in the chemical industry and in materials research, but also in disciplines such as drug development and agro-chemistry.
Quantum Biology - Last but not least, quantum physics helps us to better understand the biochemistry of life.
A few years ago bio-scientists started talking about “quantum biology”. For example, the details of photosynthesis in plants can only be understood by explicitly considering quantum effects.
And among other things, the genetic code is not completely stable, as protons in DNA are vulnerable to the tunnel effect, and it is this effect that is partly responsible for the emergence of spontaneous mutations.
Yet as always, when something is labelled with the word “quantum”, there is some fuzziness in the package.
Theoretically, the structures of atoms and molecules and the dynamics of chemical reactions can be determined by solving the Schrödinger equation (or other quantum equations) for all atomic nuclei and electrons involved in a reaction.
However, these calculations are so complicated that, using the means available today, an exact solution is possible only for the special case of hydrogen, i.e., for a system with a single proton and a single electron. In more complex systems, i.e., in practically all real applications in chemistry, the Schrödinger equation can only be solved using approximations.
And this requires the most powerful computers available today.
Theoretically, the equations of quantum theory can be used to calculate any process in the world.
However, even for simple molecules the calculations are so complex that they require the fastest computers available today, and physicists must nevertheless satisfy themselves with only approximate results.
You may also want to read more about Quantum Computing here.
