First-principles calculations

Density Functional Theory (DFT) is a powerful computational method used extensively in physics, chemistry, and materials science to study the electronic and nuclear structure of many-body systems, including atoms, molecules, and condensed phases. By using functionals, which are functions of another function, DFT can determine the properties of a many-electron system based on the electron density. In addition to its primary use as a ground-state method, DFT is also a valuable tool for exploring non-equilibrium physics. For example, it can compute phonon excitation spectra and nonlinear couplings, such as phonon-phonon interactions. The latter becomes essential for guiding and predicting experiments utilizing nonlinear phononics. In addition, DFT can accurately calculate optical response functions and their derivatives with respect to perturbations, making it an important tool for analyzing nonlinear spectroscopy results.