Dispersionkorreksjonene

Dispersionkorreksjonene refer to mathematical adjustments applied to quantum‑chemical calculations to account for van der Waals or dispersion forces, which are not adequately described by many standard electronic‑structure methods. In density functional theory (DFT), local or semi‑local exchange‑correlation functionals often underestimate long‑range correlation effects; dispersionkorreksjonene augment the Hamiltonian with an additional term that captures induced dipole–induced dipole interactions.

There are several families of these corrections. Empirical pairwise schemes, often called DFT‑D, add a summed inverse‑power‑law term to the energy, scaling with a pre‑determined dispersion coefficient \(C_{6}^{ij}\) for each atomic pair. The most common variants are DFT‑D2, DFT‑D3, and DFT‑D3(BJ), the latter including a Becke–Johnson damping function to avoid over‑counting at short distances. Non‑empirical methods, such as the exchange–hole dipole moment (XDM) or many‑body dispersion (MBD), derive the coefficients from the electron density or include higher‑order many‑body interactions, improving accuracy for large, complex systems.

These corrections are especially important for modeling molecular crystals, biomolecular assemblies, and layered materials where dispersion dominates the interaction energy. While most mainstream quantum‑chemistry packages provide built‑in dispersionkorreksjonene options, users must select the appropriate scheme based on system size, required precision, and the underlying functional.

In practice, the inclusion of dispersionkorreksjonene can change predicted geometries, binding energies, and reaction barriers by several kilocalories per mole. Researchers routinely benchmark dispersion‑corrected calculations against high‑level coupled‑cluster data or experimental measurements to validate their choice of scheme. Standards bodies such as the Journal of Chemical Theory and Computation have published comprehensive reviews, guiding community adoption of best practices.