Hydrophobic hydration at the level of primitive models

Structural changes which take place in bulk water when a molecule of an apo lar solute is brought therein are studied at a very basic elementary level. Water is modelled by two different types of extended primitive models and the solute is a hard sphere. The model mixture, which does not incorporate any water-solute interaction but the hard-core repulsion and is free of any adjustable parameter, is shown to predict the site-site correlation functi ons and details of the orientational arrangement of water molecules in the first hydration shell in full agreement with results obtained using complex realistic potentials.