Quantum chemistry, one of the main consequences of quantum mechanics
Certain phenomena discovered in the 19th century, such as black body radiation or atomic spectra, could not explain the classical mechanics formed by the laws of Newton and the laws of Maxwell's electromagnetism. In this sense, they focused on completing what we now know as quantum mechanics. A number of important milestones were set in this process. The first of these was that Max Planck pointed out in 1900 that the energy of electromagnetic radiation was quantized; that is, that the energy of radiation of a certain wavelength or frequency could not take any value, and that it had to be a multiple of E=h95 (h being the Planck constant and frequency v).
After this, in 1905, Albert Einstein explained the photoelectric effect, that is, he stated that in certain metals, electromagnetic radiation could cause the release of some electrons, and that electromagnetic radiation was composed of photons, and that when light attacked matter, each electron, taking the energy of a photon, could exit the structure of the metal if that energy exceeded a certain value.
In 1923, Louis De Broglie laid down the principle of dual membership. According to this principle, electrons and other structures at the atomic level were simultaneously wave and corpuscular in nature, and the wavelength depended on the linear momentum m·v:
λ=h/mv
This double nature made it possible to explain all the phenomena that occurred in them. For example, an electron wire passing through a slot provided diffraction patterns such as radiation.
With these principles in mind, in 1925, Werner Heisenberg and Erwin Schrödinger independently formulated what are known as Matrix Mechanics and Wave Mechanics. They also contested each other for a while, wanting to defend their own and devalue what the other had done. in 1926, however, Erwin Schrödinger himself proved that the two statements were compatible.
Finally, in 1928, Paul Dirac combined quantum mechanics with the theory of relativity, making room for spin magnitude.
The birth of quantum chemistry
It can be said that quantum chemistry itself is one of the main consequences or applications of quantum mechanics. In fact, by solving the Schrodinger equation it is possible to study the evolution of a chemical system without entering a laboratory. And this allows the study of structures that have not yet been synthesized or phenomena that cannot be obtained in the laboratory and that occur under extreme conditions. This equation, however, can only be solved analytically for single-electron systems. For the rest of the cases, different approaches have been developed.
In this sense, the Functional Density Theory (DFT) was an important milestone within quantum chemistry. through the development given by Kohn and Sham in 1965, the energy of the entire system is expressed as a functional electron density, so it is enough to know the electron density (according to three variables) instead of the coordinates of all the electrons (3N variables). The fact is that the exact form of this density function is unknown and a different function is currently used for each type of system.
Accompanied by artificial intelligence
One of the problems of quantum chemistry is its high computational cost. After all, when solving equations of quantum mechanics, it is necessary to explicitly consider the electrons of atoms. In this sense, it is now possible, through machine learning, to obtain force fields with an accuracy similar to that of DFT. This contributes significantly to the study of periodic systems of solid structures, since it would not only allow the study of larger supercells, but could also simulate much longer periods of time in molecular dynamics.
In essence, it is believed that with the computational cost of classical mechanics in this manner, results of the same precision as quantum mechanics can be obtained.
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