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Electronic Structure Calculations of Calcium Silicate Hydrates

Published online by Cambridge University Press:  15 February 2011

P. A. Sterne
Affiliation:
Department of Physics, University of California, Davis, CA 95616 Lawrence Livermore National Laboratory, Livermore, CA 94551
A. Meike
Affiliation:
Lawrence Livermore National Laboratory, Livermore, CA 94551
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Abstract

Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25°C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, we are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO3) and xonotlite (Ca6Si6O17(OH)2), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1–1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases.

Type
Research Article
Copyright
Copyright © Materials Research Society 1996

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