Kirkwood–buff integrals from molecular simulation

The Kirkwood–Buff (KB) theory is one of the most rigorous solution theories that
connects molecular structure to macroscopic behaviour. The key quantity, the so–called KB Kirkwood–Buff Integrals (KBIs), are defined either in terms of fluctuations in the number of molecules or integrals over radial distribution functions over open subvolumes. In the grand–canonical ensemble, KBIs of infinitely large and open systems are directly related to thermodynamic properties such as partial derivatives of chemical potentials and partial molar volumes. Using molecular simulations, it is only possible to study small systems with a finite number of molecules, and therefore finite–size effects should be considered.