Efficient First-Principles Calculation of the Quantum Kinetic Energy and Momentum Distribution of Nuclei

Michele Ceriotti and David E. Manolopoulos
Phys. Rev. Lett. 109, 100604 – Published 7 September 2012
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Abstract

Light nuclei at room temperature and below exhibit a kinetic energy which significantly deviates from the predictions of classical statistical mechanics. This quantum kinetic energy is responsible for a wide variety of isotope effects of interest in fields ranging from chemistry to climatology. It also furnishes the second moment of the nuclear momentum distribution, which contains subtle information about the chemical environment and has recently become accessible to deep inelastic neutron scattering experiments. Here, we show how, by combining imaginary time path integral dynamics with a carefully designed generalized Langevin equation, it is possible to dramatically reduce the expense of computing the quantum kinetic energy. We also introduce a transient anisotropic Gaussian approximation to the nuclear momentum distribution which can be calculated with negligible additional effort. As an example, we evaluate the structural properties, the quantum kinetic energy, and the nuclear momentum distribution for a first-principles simulation of liquid water.

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  • Received 23 May 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.100604

© 2012 American Physical Society

Authors & Affiliations

Michele Ceriotti* and David E. Manolopoulos

  • Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom

  • *michele.ceriotti@chem.ox.ac.uk

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Issue

Vol. 109, Iss. 10 — 7 September 2012

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