One should distinguish between coordination numbers and hydration numbers. Following Bockris

1. Description of a Chemical System as a Set of m Fixed Nuclei and n Electrons

1.1 Introduction
1.2 The SCF-LCAO-MO Approximation
1.3 The Correlation Energy Correction
1.4 Statistical Estimate of the Correlation Energy
1.5 Configuration Interaction
1.6 Combination of Statistical Methods and C.I. Techniques
1.7 Molecular Extra Correlation Energy
1.8 Choice of the Basis Set for the SCF-LCAO-MO Functions
1.9 Electron Population Analyses
1.10 Bond Energy Analyses in a Single Molecule
1.11 Bond Energy Analyses for Molecular Complexes
1.12 Bond Energy Analyses to Derive Chemical Structural Formulas
1.13 References
2. Structure of Liquid Water as a Test Case
2.1 Introduction
2.2 Approximate Hartree-Fock Potential for the Water Dimer
2.3 Polymers of Water Molecules in the Hartree-Fock Approximation
2.4 Monte Carlo Simulation of Liquid Water Using an Hartree-Fock Potential
2.5 Structure of Liquid Water Using an Accurate Potential
2.6 References
3. Coordination Numbers and Solvation Shells
3.1 Introduction
3.2 Structure of Water Arounds Ion Pairs
3.3 The Three-body Effects
3.4 More Accurate Determination of the Coordination Numbers for Ions
3.5 Solvation Potentials for Amino Acids
3.6 Conclusions
3.7 References.