How Large are Nonadiabatic Effects in Atomic and Diatomic Systems?

Abstract

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.

9 pages, 9 figures; corrected boron mass and error bars for nonadiabatic dissociation energies

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• Continuum variational and diffusion quantum Monte Carlo calculations
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Cited by in corpus (6)

• QMCPACK : An open source ab initio Quantum Monte Carlo package for the electronic structure of atoms, molecules, and solids
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• Accurate barrier heights using diffusion Monte Carlo
• Density functional theory beyond the Born-Oppenheimer approximation: accurate treatment of the ionic zero-point motion
• Nucleus-electron correlation revising molecular bonding fingerprints from the exact wavefunction factorization
• Exotic Harmonium Model: Exploring Correlation Effects of Attractive Coulomb Interaction