Finding diffusive directions in supercooled liquids by partial minimization of the potential energy

Imaginary frequency instantaneous normal modes are attractive candidates for the diffusive motions in supercooled liquids. However, two-level systems and roughness of the multidimensional potential energy (U) landscape lead to Im −ω modes unrelated to diffusion. It is shown that a small number (3 or 4) of steps taken while seeking a minimum of U removes such artifacts and leads to excellent diffusive modes. In general the time- and minimization step-dependent U(n,t) reveals a detailed picture of supercooled dynamics in terms of the landscape.