Negative thermal expansion (NTE) is crucial for controlling the thermomechanical properties of functional materials, albeit being relatively rare. This study reports a giant NTE (aV=-9.2·10-5 K-1, 100-200 K; aV=-3.7·10-5 K-1, 200-650 K) observed in NaB(CN)4, showcasing interesting ultralight properties. A comprehensive investigation involving synchrotron X-ray diffraction, Raman spectroscopy, and first-principles calculations has been conducted to explore the thermal expansion mechanism. The findings indicate that the low-frequency phonon modes play a primary role in NTE, and non rigid vibration modes with most negative Grüneisen parameters are the key contributing factor to the giant NTE observed in NaB(CN)4. This work presents a new material with giant NTE and ultralight mass density, providing insights for the understanding and design of novel NTE materials.

Giant Negative Thermal Expansion in Ultralight NaB(CN)4

Sanson, Andrea;
2024

Abstract

Negative thermal expansion (NTE) is crucial for controlling the thermomechanical properties of functional materials, albeit being relatively rare. This study reports a giant NTE (aV=-9.2·10-5 K-1, 100-200 K; aV=-3.7·10-5 K-1, 200-650 K) observed in NaB(CN)4, showcasing interesting ultralight properties. A comprehensive investigation involving synchrotron X-ray diffraction, Raman spectroscopy, and first-principles calculations has been conducted to explore the thermal expansion mechanism. The findings indicate that the low-frequency phonon modes play a primary role in NTE, and non rigid vibration modes with most negative Grüneisen parameters are the key contributing factor to the giant NTE observed in NaB(CN)4. This work presents a new material with giant NTE and ultralight mass density, providing insights for the understanding and design of novel NTE materials.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3514873
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