Abstract

Density Functional Theory (DFT) has proven to be one of the most successful theoretical and computational frameworks over the past two decades, with more than 40,000 papers related to DFT published each year and the number still growing rapidly. Although DFT is grounded in quantum mechanics and was originally developed by physicists, it has had a major impact across the broader scientific community, spanning chemistry, materials science, and even environmental science; by the end of 2025, its most widely used software package, VASP , was used by more than 4,000 research groups worldwide.

In this seminar, I will introduce the key idea behind DFT —replacing the exponentially complex many-electron wavefunction with the electron density—and explain how the Kohn–Sham approach makes the problem computationally tractable while retaining useful accuracy. I will then discuss what DFT can (and cannot) reliably deliver in surface-physics research: equilibrium structures, total energies and energy differences, charge densities, electronic band structures and densities of states, and, through standard extensions such as density-functional perturbation theory (DFPT) and finite-displacement methods, vibrational and phonon properties.