Home › Forums › density functional theory › the Born-Oppenheimer approximation › Where the Born-Oppenheimer approximation is not valid This topic has 0 replies, 1 voice, and was last updated 1 year, 1 month ago by George-Andreev. Viewing 1 post (of 1 total) Author Posts October 24, 2023 at 3:06 pm #9664 George-AndreevParticipant Those cases are: – mass of nuclei is equal to mass of electron (within one order of magnitude) – speed of nuclei is non-negligible (e.g. high temperature) Author Posts Viewing 1 post (of 1 total) You must be logged in to reply to this topic. Log In Username: Password: Keep me signed in Log In