täthetsfunktionalteorin

Density-functional theory (DFT) is a quantum mechanical modeling method used to investigate the electronic structure of materials. It is a powerful tool for calculating the ground-state properties of a many-electron system. The core idea of DFT is that the ground-state energy of an interacting system of electrons can be determined solely from the electron density, a three-dimensional function that depends only on the positions of the electrons. This significantly simplifies the problem compared to traditional wavefunction-based methods, which involve the much more complex many-body wavefunction.

The development of DFT is largely credited to Walter Kohn and his collaborators. Kohn received the Nobel Prize in Chemistry in 1998 for his work on DFT. The theory is based on two fundamental theorems: the Hohenberg-Kohn theorems. The first theorem states that the ground-state energy and all other ground-state properties of a system are unique functionals of the electron density. The second theorem establishes that the ground-state energy is the minimum value of the energy functional when evaluated with the true ground-state electron density.

In practice, DFT calculations often employ approximations for the exchange-correlation functional, which accounts for the quantum mechanical effects of electron exchange and correlation. The accuracy of DFT results depends heavily on the quality of the chosen approximation. Despite these approximations, DFT has proven to be remarkably successful across a wide range of scientific disciplines, including condensed matter physics, chemistry, and materials science, for predicting properties such as bonding energies, structural parameters, and electronic band structures.