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Title: How large are nonadiabatic effects in atomic and diatomic systems?

With recent developments in simulating nonadiabatic systems to high accuracy, it has become possible to determine how much energy is attributed to nuclear quantum effects beyond zero-point energy. In this work, we calculate the non-relativistic ground-state energies of atomic and molecular systems without the Born-Oppenheimer approximation. For this purpose, we utilize the fixed-node diffusion Monte Carlo method, in which the nodes depend on both the electronic and ionic positions. We report ground-state energies for all systems studied, ionization energies for the first-row atoms and atomization energies for the first-row hydrides. We find the ionization energies of the atoms to be nearly independent of the Born-Oppenheimer approximation, within the accuracy of our results. The atomization energies of molecular systems, however, show small effects of the nonadiabatic coupling between electrons and nuclei.
Authors:
; ;  [1] ;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Physics, University of Illinois, Urbana, Illinois 61801 (United States)
  2. (Finland)
  3. Oak Ridge National Laboratory, Materials Sciences & Technology Division, Oak Ridge, Tennessee 37831 (United States)
  4. Department of Chemistry, University of Illinois, Urbana, Illinois 61801 (United States)
Publication Date:
OSTI Identifier:
22489642
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; ATOMIZATION; ATOMS; BORN-OPPENHEIMER APPROXIMATION; COUPLING; DIFFUSION; ELECTRONS; GROUND STATES; HYDRIDES; MONTE CARLO METHOD; NUCLEI; RELATIVISTIC RANGE