Study of the structure of molecular complexes. Coordination numbers for Li +, Na +, K +, F − and Cl − in water

Abstract

A cluster of 200 water molecules containing a single ion (either Li + or Na + or K + or F − or Cl −) has been studied at T = 298 K using Monte Carlo techniques. The waterwater interaction is obtained from a quantum-mechanical study of CI type; the ionwater potentials have been obtained from HartreeFock type computations. The computed coordination numbers in the first shell for Li +, Na +, K +, F − and Cl − are 4.0, 4.3, 5.1, 3.85 and 4.3, respectively; the corresponding first hydration shell radii are 2.28 Å, 2.59 Å, 3.27 Å, 1.99 Å and 2.85 Å, respectively. A discussion of the second and third hydration shell radii and coordination numbers is given.