Because of the fundamental importance of water in the
physical and biological sciences, understanding its microscopic
structure is an issue of long-standing interest.
Elucidating the local environment of the protons is particularly
intriguing due to their crucial role in hydrogen
bonding. Nuclear quantum effects significantly impact the
behavior of water, which is indicated by the variation of
many properties when protons are substituted with deuterium
(D) or tritium (T). For example, the melting point of
heavy water (D2O) is 3.82 K higher than that of light (H2O)
water, and this effect is more pronounced in tritiated water
(T2O) [1], providing evidence that quantum effects destabilize
the hydrogen bond network.