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Computer calculation of water-clay interactions using atomic pair potentials
Published online by Cambridge University Press: 09 July 2018
Abstract
Existing data on interatomic potentials have been used to study the interactions between an uncharged clay sheet and a water molecule. Calculations show that most of the clay surface is relatively hydrophobic, with binding energies for a water molecule in the range 1·0–4·5 kcal mol−1. There is, however, a low-energy site for an oriented water molecule above the layer OH group and within the ring of six SiO4 tetrahedra. Using two different models for the interactions, the binding energy in this position is found to be either 13·2 or 21·8 kcal mol−1. The existence of the low-energy site accounts for the formation of the hydrated ‘10 Å’ phase of talc, which is known from high-pressure experiments. Data on the PT stability of this phase can be used to estimate its energy of dehydration. This quantity is shown to be consistent with the value of 21·8 kcal mol−1 for the binding energy of a water molecule and the energy associated with the expansion of the layers from the 9·35 Å phase.
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- Copyright © The Mineralogical Society of Great Britain and Ireland 1989
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