Thermal expansion of continuous random networks of carbon

Abstract Homogeneous and isotropic continuous random networks (CRNs) of carbon were created spanning a large portion of hybridization space, from s p 3 -rich configurations up to 70% s p 2 carbon. For each of these CRNs, the volumetric coefficient of thermal expansion (CTE) was calculated according to the quasi-harmonic approximation using the Brenner potential. The CTE of H-free, s p 3 -rich CRNs is similar to that of diamond and almost constant up to about 50% s p 2 -C. The CTE at 300 K varies from about 3.5 × 10 − 6 K − 1 to 5.5 × 10 − 6 K − 1 , linearly increasing with the s p 2 -C content for CRNs above ca. 40% s p 2 -C, in good agreement with previous experimental studies. A small fraction of 10% to 15% of the CRNs, irrespective of composition, exhibit volumetric negative thermal expansion (NTE) over a limited temperature range around 100 K to 200 K.