Phase transition kinetics revealed by in situ x-ray diffraction in laser-heated dynamic diamond anvil cells

We report successful coupling of dynamic loading in a diamond anvil cell and stable laser heating, which enables compression rates up to 500 GPa/s along high-temperature isotherms. Dynamic loading in a diamond-anvil cell allows exploration of a wider range of pathways in the pressure-temperature space compared to conventional dynamic compression techniques. By x-ray diffraction, we are able to characterize and monitor the structural transitions with the appropriate time resolution i.e., millisecond timescales. Using this method, we investigate the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>γ</a:mi><a:mtext>−</a:mtext><a:mi>ε</a:mi></a:mrow></a:math> phase transition of iron under dynamic compression, reaching compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results demonstrate a distinct response of the <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi>γ</b:mi><b:mtext>−</b:mtext><b:mi>ε</b:mi></b:mrow></b:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>α</c:mi><c:mtext>−</c:mtext><c:mi>ε</c:mi></c:mrow></c:math> transitions to the high compression rates achieved, possibly due to the different transition mechanisms. These findings open up new avenues to study tailored dynamic compression pathways in the pressure-temperature space and highlight the potential of this platform to capture kinetic effects (over ms time scales) in a diamond anvil cell. Published by the American Physical Society 2024