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Free energy calculations involving NH 4 + in water
Author(s) -
Boudon Stéphane,
Wipff Georges
Publication year - 1991
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540120106
Subject(s) - chemistry , water model , monte carlo method , thermodynamics , molecular dynamics , solvation , solvent , computational chemistry , physics , organic chemistry , statistics , mathematics
The analysis of the hydration of NH 4 + and the estimation of relative or absolute free energies of hydration by means of Monte Carlo computer simulations using different 1‐6‐12 potential functions is reported. Two electrostatic representations of NH 4 + (used respectively by W.L. Jorgensen and P.A. Kollman) in conjunction with two common water models (TIP3P and TIP4P) are considered. A change in relative hydration free energies of 1.7 kcal/mol is found when the NH 4 + models are mutated into each other in either TIP3P or TIP4P. The NH 4 + → Na + mutation in both solvent models leads to similar but overestimated relative hydration energies of about −28.7 kcal/mol. Similarly, the NH 4 + annihilation significantly overestimates the absolute free energy of hydration.