Isobaric process

Chemical physics

Materials science

Supercooling

Specific heat

Thermodynamics

Physics

Heat capacity

Calorimetry

Liquid water

Molecular dynamics

Work (physics)

Computational chemistry

Evaporation

Freezing point

Chemistry

Water model

Proceedings of the National Academy of Sciences

Significance The importance of molecular understanding of the structure, dynamics. and properties of liquid water is recognized in many scientific disciplines. Here, we study experimentally the structure and thermodynamics of bulk liquid water as it is supercooled by evaporation down to ∼228 K. The unique aspect of this work is the use of ultrafast calorimetry that enables us to determine the specific-heat capacity of water to unprecedentedly low temperatures. The observed maximum of about 218 J/mol/K at 229 K is consistent with the liquid–liquid critical point model and supports a proposed fragile-to-strong transition at ∼220 K to explain the steep decrease in the estimated self-diffusion coefficient below 235 K.

Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry