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arXiv · 1507.05959

How Large are Nonadiabatic Effects in Atomic and Diatomic Systems?

Yubo Yang·Ilkka Kylanpaa·Norm Tubman·Jaron Krogel·Sharon Hammes-Schiffer·David Ceperley
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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.

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Yubo Yang, Ilkka Kylanpaa, Norm Tubman, Jaron Krogel, Sharon Hammes-Schiffer, David Ceperley. 2015-07-21. How Large are Nonadiabatic Effects in Atomic and Diatomic Systems?. https://doi.org/10.1063/1.4931667

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