Fig. 8. Field-free and in-field IR spectra of liquid water.

a Comparison of experimental⁷⁷ (Expt) and three thermostated ring polymer molecular dynamics (TRPMD) based infrared (IR) spectra of liquid water in the absence of electric field at 300 K, computed with force-only training (FIREANN-wF) and brute-force dipole training (FIREANN-wD) based on the field-induced recursively embedded atom neural network model, and on-the-fly calculations at the same computational level extracted from ref. ⁷⁵ (On-the-fly). b Comparison of TRPMD-based IR spectra of liquid water obtained from the FIREANN-wF model with electric fields of 0.0 V Å⁻¹, 0.2 V Å⁻¹, and 0.4 V Å⁻¹ along the x direction. Source data are provided as a Source Data file.