Origin of the colossal positive and negative thermal expansion in Ag3[Co(CN)6]: an ab initio density functional theory study

Calleja, M. and Goodwin, A. L. and Dove, M. T. (2008) Origin of the colossal positive and negative thermal expansion in Ag3[Co(CN)6]: an ab initio density functional theory study. Journal of Physics: Condensed Matter, 20 (25). p. 255226. DOI 10.1088/0953-8984/20/25/255226

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Official URL: http://dx.doi.org/10.1088/0953-8984/20/25/255226

Abstract

DFT calculations have been used to provide insights into the origin of the colossal positive and negative thermal expansion in Ag3[Co(CN)6]. The results confirm that the positive expansion within the trigonal basal plane and the negative expansion in the orthogonal direction are coupled due to the existence of a network defined by nearly rigid bonds within the chains of Co–C–N–Ag–N–C–Co linkages. The origin of the colossal values of the coefficients of thermal expansion arise from an extremely shallow energy surface that allows a flexing of the structure with small energy cost. The thermal expansion can be achieved with a modest value of the overall Gr¨uneisen parameter. The energy surface is so shallow that we need to incorporate a small empirical dispersive interaction to give ground-state lattice parameters that match experimental values at low temperature. We compare the results with DFT calculations on two isostructural systems: H3[Co(CN)6], which is known to have much smaller values of the coefficients of thermal expansion, and Au3[Co(CN)6], which has not yet been synthesized but which is predicted by our calculations to be another candidate material for showing colossal positive and negative thermal expansion.

Item Type: Article
Uncontrolled Keywords: 08AREP IA56 2008 P
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Journal of Physics: Condensed Matter
Volume: 20
Page Range: p. 255226
Identification Number: 10.1088/0953-8984/20/25/255226
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:01
Last Modified: 23 Jul 2013 10:01
URI: http://eprints.esc.cam.ac.uk/id/eprint/180

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