Home › Forums › density functional theory › the Born-Oppenheimer approximation › Born-oppenheimer This topic has 0 replies, 1 voice, and was last updated 2 years, 2 months ago by Tristan Boen. Viewing 1 post (of 1 total) Author Posts October 4, 2022 at 9:33 am #6860 Tristan BoenParticipant The Born-Oppenheimer Approximation will not be valid when the two masses are of similar weight. So when the center of mass is not very close or inside the bigger mass. 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