Elastic constant C_(11) of ~(12)C diamond between 10 and 613 K

摘要

We measured the temperature dependence of the elastic constant C_(11) of a ~(12)C diamond monocrystal using picosecond ultrasonics between 10 and 613 K. We found that C_(11) is almost temperature independent below room temperature; the temperature coefficient around 300 K is -6.6 MPa/K. Our results show a significantly higher Einstein temperature than reported values by ～30%, indicating that diamond has a larger zero-point energy, which remains dominant around ambient temperature. We also calculated the temperature dependence of the elastic constants using ab-initio methods, resulting in good agreement with measurements. Our study shows that below-ambient-temperature measurements are not sufficient to extract the Debye temperature and the Griineisen parameter of high-Debye-temperature materials.