THE VIRTUAL MATTER LABORATORY

New types of computer simulation are being used to investigate matter on the atomic scale. Unlike older simulation methods, the new techniqu es represent a solid or a liquid as a collection of nuclei and electro ns, and the laws of quantum mechanics are used to calculate the energy and the forces from first principles. The most successful method so f ar for doing first-principles simulation is based on density functiona l theory and the pseudopotential approximation. I describe the main id eas of these techniques and explain how they can be used to perform si mulations in which chemical bonds are made and broken. I give illustra tions of current work in two areas: the atomic-scale behaviour of wate r and other liquids; and molecular processes at surfaces. I stress tha t the new methods are still evolving rapidly and I point to likely dev elopments in the next few years.