Abstract

Due to its favorable system-size scaling, time-dependent density functional theory within an Ehrenfest scheme is often used to simulate coupled electron-ion dynamics. This can be done in two ways that are in principle identical: propagating time-dependent electronic Kohn-Sham equations or propagating electronic coefficients on surfaces obtained from linear-response. We discuss how use of an approximate functional in practise leads to qualitatively different dynamics in the two approaches due to their probing of the functional in different domains and show why the latter approach is more accurate. The general idea has implications for any non-perturbative dynamics simulations using TDDFT : if you can reformulate it in terms of linear response quantities, your results will be more reliable.