PHYSICAL PROPERTIES. “A more subtle effect of deuteration is the formation of slightly stronger hydrogen (or deuterium) bonds in D2O as compared to H2O3. This results in a small increase of the freezing and boiling points by 3.8 °C and 1.4 °C, respectively, and in a slight increase of 0.44 in pH (or pD) of pure water upon deuteration.”
https://www.nature.com/articles/s42003-021-01964-y