Unusual thermal expansion in organic molecular crystals: a rare phenomenon

This paper provides a brief insight into thermal expansion of organic molecular crystals with reference to the recent article by Andrew Bond published in Acta Crystallographica on a CSD survey of thermal expansion in organic molecular crystals. An unusual phenomenon occurs when a material contracts upon heating known as Negative Thermal Expansion (NTE). Unusual thermal expansion may also occur in cases of neither expansion or contraction of a material which is known as Zero Thermal Expansion (ZTE). Electronic engineering and precision instruments, design of materials with desired thermal expansion is highly challenging because the underlying mechanism for NTE varies from material to material, while the study of thermal expansion is extremely important to understand the structural safety and accuracy in many engineering fields, such as aerospace, civil. The e article by Bond addresses the general distribution of coefficients of thermal expansion (CTE) of specifically organic crystalline compounds by systematic analysis of variable-temperature single-crystal X-ray diffraction data available in the Cambridge Structural Database (CSD).