Dynamic compression and pressure cycling in dynamic diamond anvil cells: MgO and neon studied by time-resolved x-ray diffraction

Static compression experiments using diamond anvil cells (DAC), combined with x-ray diffraction (XRD) are widely used to study material properties at extreme pressures. Recent advances enable time-resolved XRD during dynamic compression along tailored loading paths. However, the influence of compression rate on derived properties remains poorly understood, and the use of tailored compression paths—particularly pressure cycling—requires further investigation. Here, we employed time-resolved XRD in a dynamic DAC to compress MgO in a Ne pressure medium along a tailored compression path consisting of a ramp, plateau, and cyclic loading. Pressure-volume relations derived from ramp compressions at average compression rates of 0.22 and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mn>0.46</a:mn> <a:mspace width="0.16em"/> <a:mi>GPa</a:mi> <a:mspace width="0.16em"/> <a:msup> <a:mrow> <a:mi mathvariant="normal">s</a:mi> </a:mrow> <a:mrow> <a:mo>−</a:mo> <a:mn>1</a:mn> </a:mrow> </a:msup> </a:mrow> </a:math> agree closely with previous static experiments, with minor but detectable systematic deviations in the faster compression run. Stress analysis suggests that this deviation might be related to an increased flow strength of Ne under fast compression. During the postramp plateaus, MgO pressures continued to increase, highlighting the effect of compression rate on the time required for the coupled mechanical DAC system to reach equilibrium. Under cyclic loading, we observe phase shifts between oscillating differential stresses and volume strains in Ne, possibly indicating that viscoelastic/-plastic behavior of either Ne or the gasket material contributed to the overall response. We found this effect more pronounced for lower frequencies and larger cycling amplitudes. The findings presented in this paper improve our understanding of material behavior during dynamic loading in the DAC and provide reference data and methodology for studies of complex materials and loading paths.