Experimental evidence of a liquid-liquid critical point in supercooled water
Summary
The search for the liquid-liquid critical point in supercooled water is challenging owing to rapid crystallization. We studied supercooled water at timescales before ice formation by heating high- and low-density amorphous ices using infrared ultrafast laser pulses, followed by x-ray scattering. By varying the pump laser fluence, we accessed liquid states straddling the predicted critical point. We observed a crossover from a discontinuous to a continuous transition at which broad and slow
Content
# Experimental evidence of a liquid-liquid critical point in supercooled water
*Published: 2026 Mar 26*
The search for the liquid-liquid critical point in supercooled water is
challenging owing to rapid crystallization. We studied supercooled water at
timescales before ice formation by heating high- and low-density amorphous ices
using infrared ultrafast laser pulses, followed by x-ray scattering. By varying
the pump laser fluence, we accessed liquid states straddling the predicted
critical point. We observed a crossover from a discontinuous to a continuous
transition at which broad and slow structural variations occurred, consistent
with critical fluctuations and slowing down. We also observed a rapid increase
in the heat capacity indicating a critical divergence at 210 ± 8 K coincident
with enhanced density fluctuations. These results suggest that our experiments
have directly probed the vicinity of a critical point in supercooled water.
DOI: 10.1126/science.aec0018