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Density Functional Theory Study of The Decomposition of Mg(OH)2: a Lamellar Dehydroxylation Model

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Wed, 2015-07-15 10:06 — Hamdallah Bearat
Journal Title, Volume, Page: 
Materials Chemistry and Physics, Volume 77, Issue 2, 15 January 2003, Pages 416–425
Year of Publication: 
2003
Link: 
http://www.sciencedirect.com/science/article/pii/S0254058402000202
Authors: 
A.V.G. Chizmeshya
Center for Solid State Science, Arizona State University, Tempe, AZ 85287, USA
M.J. McKelvy
Center for Solid State Science, Arizona State University, Tempe, AZ 85287, USA
R. Sharma
Center for Solid State Science, Arizona State University, Tempe, AZ 85287, USA
R.W. Carpenter
Center for Solid State Science, Arizona State University, Tempe, AZ 85287, USA
Hamdallah A. Béarat
Center for Solid State Science, Arizona State University, Tempe, AZ 85287, USA
Current Affiliation: 
Department of Materials Science, Faculty of Engineering and Information Technology, An-Najah National University, Nablus. Palestine
[email protected]
Preferred Abstract (Original): 

We present a density functional theory investigation of the decomposition of Mg(OH)2. Based on recent experiments indicating a lamellar dehydroxylation process we have calculated the energetics, elastic behavior and structural trends of a series of oxyhydroxide intermediates of composition Mgx+yOx(OH)2y representing a solid solution series between brucite (Mg(OH)2) and periclase (MgO). Using a variationally induced breathing (VIB) ionic approach we find that this broad range of lamellar oxyhydroxide intermediate materials becomes thermodynamically accessible at temperatures near 500 °C. The computed dehydroxylation dependence of the compressibility is found to vary dramatically with the initial formation of periclase-like oxide layers displaying an abrupt jump to a value near that of periclase (∼160 GPa). In contrast to this very non-linear behavior the basal plane lattice parameter a is found to exhibit a nearly linear (Vegard-like) dependence on hydroxyl content.