Fig. 6: TRPMD simulations of ammonia using NNQMD.

a Allegro model for NNQMD. b Comparison of computed vibrational spectrum using Allegro TRPMD and VISION spectrum which shows excellent agreement. DFT results at 0 K (blue color) are shown for comparison. c Comparison of classical and TRPMD simulation of high-energy N-H stretching modes. Merging of Symmetric and Anti-symmetric splitting agrees with SEQUOIA experiment. d INS computation of spectrum near N-H stretching peak from summing only single phonon scattering and with inclusion of multi-phonon scattering. e TRPMD ND3 VDOS for high-energy N-D stretch where peak splitting remains. f Computation of VDOS for NH3 liquid state, in which low energy peaks are all washed out. g Computed hardening of N-H stretching modes of NH3 in liquid state consistent with SEQUOIA experiment.