What is Quantum Chemistry and How Do We Use It?

We have all heard of chemistry and probably studied it a bit to some academic degree, but you have probably never heard of quantum chemistry. It is a very specific part of chemistry that has carried out important research. Let’s get to know a little about this part of science.

Quantum chemistry is a branch of chemistry that makes use of physics, and specifically quantum mechanics. This part of science studies chemical systems and also allows us to have a better understanding of molecules.

Molecules, although they are part of the physical world around us, are different in many ways. It must be clear that these particles are very small and are made up of even smaller particles, which are electrons, protons, etc. These small particles follow different laws from the ones we see all the time, and that govern things like energy or motion (classical laws), these are the laws of quantum theory.

This theory was born in the last century (20th century). It came about in a revolutionary way in physics and chemistry since before it, links between molecules and other behaviours were not explained, that is why when it arrived it became a watershed to understand better the atoms and molecules that makeup materials. Before quantum theory, all the information was qualitative and not very accurate. Although there were experimental investigations in those times, the results of such experiments were reported without knowing or explaining the behaviour of molecules, since the mechanisms of action were unintelligible. For these reasons, many investigations were not predictable.

In many experiments, the factors that caused certain reactions to pass or stop were only vaguely known, such as the case of phosphorescence, fluorescence, and bioluminescence. It was deduced, for example, that certain materials were capable of absorbing and retaining specific types of light under certain conditions, but how this occurred and how such combinations might have been made to provoke this reaction was not known at all. It was simply speculated that some molecules emitted light spontaneously. At the arrival of quantum chemistry, this could be done perfectly, and the reason for many chemical manifestations was understood.

This branch of chemistry covers the understanding of many processes in research, and one case where it has helped a lot is in pharmacology. In this branch, the prediction of chemical compromises is widely used. Within the design of medicines, there are only two options.

1. Obtain new products in laboratories and analyze their behaviour and characteristics to determine if their use in the medical world is possible.
2. Use quantum chemistry, helping to predict certain molecular behaviours to discard molecules that do not serve us to synthesize a drug. 

In some way, we can say that chemistry is consolidated as a true science with predictive capacity from the development of quantum chemistry.

The best known field related to the quantum topic is physics, which although many do not even know what it is about, surely all have heard its name on some occasion. It is the opposite with quantum chemistry, which is practically unknown. The reason this happens is that this branch of chemistry is very specialized and requires very advanced knowledge in other sciences such as computer science and mathematics to be able to understand it.

Although it was at the beginning of the 20th century when this science was born, it was not until the end of the century that it became a little better known, and all thanks to John Pople. He received the 1998 Nobel Prize for creating a molecular calculation computer program that allows you to perform certain calculations and predictions even without knowing in-depth about chemistry or quantum sciences. This allowed many advances, and eyes turned to see a little about this science that was hidden in the corner.

But to be a true quantum chemist you need to be a chemist; knowing physics, both electromagnetism and quantum mechanics; a good portion of mathematics because the mathematical apparatus behind it is vast and computer knowledge because the use of powerful computers is a fundamental requirement in the calculations that are carried out. For this reason, its development is also closely linked to the advancement of computers, which increasingly expands the possibilities of calculation. And despite being such a specialized science, every day, more advances are made, and more people are interested in this kind of topic.

The ways in which we can apply this science are many, although it is a science that requires specialized knowledge, many things can be done with it, such as:

• It allows studying the chemical reactivity or ability of the molecules of a substance to react with other molecules of the same or another substance
• It can be used to predict how the resulting product will be after the reactions and determine the reaction intermediates and possible by-products of the same
• Allows the study of molecular spectroscopy or the interaction of light with molecules, with application in astrophysics
• Allows predicting some properties that are later important for the design of industrial equipment

Despite being a very complex science conceptually, quantum chemistry is an exciting branch of chemistry with many applications.

Bottom Line

Quantum chemistry is a relatively new branch of chemistry, where molecular systems are studied. This is of great importance because it allows understanding the interactions between molecules and allows scientific development in many aspects. It is undoubtedly a very interesting and complex subject, and they will continue to develop projects that enable us to better understand the nature of our universe.