Evidence for instantaneous resonant modes in dense fluids with repulsive Lennard-Jones force

In terms of instantaneous-normal-mode (INM) analysis and a newly defined measure for quasilocalization, we present the evidence for the resonant modes in a model fluid, in which the pair interaction is merely the repulsive portion of the Lennard-Jones potential. We name such a quasilocalized INM as an instantaneous resonant mode (IRM). By examining the potential energy profile beyond the INM approximation, we conclude that the IRMs occur in single-well potentials with strong enough anharmonicity.