Table 1.

Competing interactions in liquid water, which governs the re-orientation dynamics under an externally applied electric field of magnitude E.

	Energy/KT298.15
K.E. per rotational DOF*	0.5
Hydrogen bond energy	8.1 (ref. 24)
μE (E = 4.3 × 108 Vm−1)	0.8
μE (E = 4.3 × 109 Vm−1	8.2

The norm of the molecular dipole is taken as μ = μ₀ + αE, where the field-free dipole (μ = 2.10 D) is the dynamic dipole as defined by⁶⁰, whereas α is the polarizability of an isolated molecule at equilibrium geometry (9.785 a.u.⁶¹). Unlike other definitions of condensed phase molecular dipoles that rely on a partitioning of the electron density, the dynamical molecular dipole is based on the coupling of an external electric field with the molecular motion, and is thus specifically relevant for this analysis. The value of the HB energy is the ensemble-average from previous condensed phase calculations employing ALMO-EDA with the same computational setup as the one used here²⁴.

^*Degree of Freedom.