Unexpected Strength of Noble Gas Solids in Diamond Anvil Cells

The stress state inside a diamond anvil cell (DAC) during high-pressure experiments involves a diverse combination of six-dimensional uniaxial shear and compressive strains, ultimately generating a complex and nonhydrostatic state. To ensure experiments are performed under (quasi-)static pressure conditions, noble gases (NGs) are usually used as pressure transmission media (PTMs). Here, this study comprehensively investigates the ultimate mechanical strength of NG solids at high pressures using first-principles calculations; specifically, this study examines the stress response of NGs under shear strains to determine nonhydrostatic pressures that may be created when NG solids are used as PTMs in high-pressure experiments. Our results show that NG solids can provide good hydrostatic conditions for samples at relatively moderate pressures, while nonhydrostatic pressure inside DAC would be widespread and nonignorable under ultrahigh high-pressure conditions. Our results theoretically indicate that during high-pressure experiments, He is an ideal candidate as a PTM under relatively low-pressure conditions (<15 GPa), but Ne shows the best performance at higher pressure. The current work offers insights into the fundamental structural and physical properties of the NG solids and enriches a fundamental understanding of the nonhydrostatic effects of broadly defined strains on modulating the physical and chemical properties of functional materials.