Ultrasound elasticity of diamond at gigapascal pressures

Diamond is the hardest known material in nature and features a wide spectrum of industrial and scientific applications. The key to diamond's outstanding properties is its elasticity, which is associated with its exceptional hardness, shear strength, and incompressibility. Despite many theoretical works, direct measurements of elastic properties are limited to only similar to 1.4 kilobar (kb) pressure. Here, we report ultrasonic interferometry measurements of elasticity of void-free diamond powder in a multianvil press from 1 atmosphere up to 12.1 gigapascal (GPa). We obtained high-accuracy bulk modulus of diamond as K-0 = 439.2(9) GPa, K-0' = 3.6(1), and shear modulus as G(0) = 533(3) GPa, G(0)' = 2.3(3), which are consistent with our first-principles simulation. In contrast to the previous experiment of isothermal equation of state, the K-0' obtained in this work is evidently greater, indicating that the diamond is not fully described by the n-m Mie-Gruneisen model. The structural and elastic properties measured in this work may provide a robust primary pressure scale in extensive pressure ranges.

Automated summary

Diamond, known as the hardest material in nature, exhibits exceptional properties due to its elasticity, including outstanding hardness, shear strength, and incompressibility. The study presented accurate elasticity measurements of diamond powder, revealing that diamond's elastic properties may not be fully described by traditional models.