Molecular Simulation – A Primer

Quantum chemistry allows us to calculate molecular properties with arbitrary accuracy: potential surface, geometry, moments, spectra, etc. However, there are properties which do not depend on a single molecule alone but can only be defined for an ensemble of many molecules: melting point, diffusion coefficient, density, for example. “Many molecules” can refer to a few dozen molecules in a molecular cluster but can also mean Avogadro’s number.