Displaced Path Integral Formulation for the Momentum Distribution of Quantum Particles
2010; American Physical Society; Volume: 105; Issue: 11 Linguagem: Inglês
10.1103/physrevlett.105.110602
ISSN1092-0145
AutoresLin Lin, Joseph A. Morrone, Roberto Car, Michele Parrinello,
Tópico(s)Climate variability and models
ResumoThe proton momentum distribution, accessible by deep inelastic neutron scattering, is a very sensitive probe of the potential of mean force experienced by the protons in hydrogen-bonded systems. In this work we introduce a novel estimator for the end-to-end distribution of the Feynman paths, i.e., the Fourier transform of the momentum distribution. In this formulation, free particle and environmental contributions factorize. Moreover, the environmental contribution has a natural analogy to a free energy surface in statistical mechanics, facilitating the interpretation of experiments. The new formulation is not only conceptually but also computationally advantageous. We illustrate the method with applications to an empirical water model, ab initio ice, and one dimensional model systems.
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