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Title: Maximizing negative thermal expansion via rigid unit modes : a geometry-based approach
Authors: Grima, Joseph N.
Bajada, Mark
Scerri, Simon
Attard, Daphne
Dudek, Krzysztof
Gatt, Ruben
Keywords: Expansion (Heat)
Materials -- Thermal properties
Rigidity (Geometry)
Chemical models
Issue Date: 2015-07
Publisher: The Royal Society of London
Citation: Grima, J. N., Bajada, M., Scerri, S., Attard, D., Dudek, K., & Gatt, R. (2015). Maximizing negative thermal expansion via rigid unit modes : a geometry-based approach. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 471(2179), 1-13.
Abstract: Existent rigid unit mode (RUM) models based on rotating squares, which may explain the phenomenon of negative thermal expansion (NTE), are generalized so as to assess the NTE potential for novel systems made from rectangular or rhombic rigid units. Analytical models for the area coefficients of thermal expansion (CTE) of these innovative networks are derived in an attempt to determine the optimal geometrical parameters and connectivity for maximum NTE. It was found that all systems exhibit NTE, the extent of which is determined by the shape and connectivity of the elemental rigid units (side lengths ratio or internal angle). It was also found that some of the networks proposed here should exhibit significantly superior NTE properties when compared with the well-known network of squares, and that for optimal NTE characteristics, pencil-like rigid units should be used rather than square-shaped ones, as these permit larger pore sizes that are more conducive to NTE. All this compliments earlier work on the negative Poisson's ratio (auxetic) potential of such systems and may provide a route for the design of new materials exhibiting superior thermo-mechanical characteristics including specifically tailored CTEs or giant NTE characteristics.
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Scholarly Works - FacSciMet

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