Analytical potential energy function for the ground state % MathType!MTEF!2!1!+- % feaagaart1ev2aaatCvAUfKttLearuqr1ngBPrgarmWu51MyVXguY9 % gCGievaerbd9wDYLwzYbWexLMBbXgBcf2CPn2qVrwzqf2zLnharyav % P1wzZbItLDhis9wBH5garqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC % 0xbbL8F4rqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs0-yq % aqpepae9pg0FirpepeKkFr0xfr-xfr-xb9adbaqaaeGaciGaaiaabe % qaamaaeaqbaaGcbaGaeiikaGsegeKCPfgBaGGbaiqa-Hfagaacamaa % CaaaleqabaGaa8xmaaaakiaa-feadaWgaaWcbaGaa8xmaaqabaGccq % GGPaqkaaa!4312! $$ (\tilde X^

Abstract

The present work is to construct the potential energy function of isotopic molecules. The so-called molecular potential energy function is the electronic energy function under Born-Oppenheimer approximation, in which the nuclear motions (translational, rotational and vibration motions) are not included, therefore, its nuclear vibration motion and isotopic effect need to be considered. Based on group theory and atomic and molecular reactive statics (AMRS), the reasonable dissociation limits of D 2 O (X A ) 1 1 are determined, its equilibrium geometry and dissociation energy are calculated by density-functional theory (DFT) B3lyp, and then, using the many-body expansion method the potential en- ergy function of D 2 O (X A )1 1 is obtained for the first time. The potential contours are drawn, in which it is found that the reactive channel D + OD→D 2 O has no threshold energy, so it is a free radical reaction. But the reactive channel O + DD→D 2 O has a saddle point. The study of collision for D 2 O (X A )1 1 is under way. D 2 O 1 1 (X A ), isotopic effect, many-body expansion theory, analytical potential energy function