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Issue 2, 2016
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Modeling quantum nuclei with perturbed path integral molecular dynamics

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Abstract

The quantum nature of nuclear motions plays a vital role in the structure, stability, and thermodynamics of molecules and materials. The standard approach to model nuclear quantum fluctuations in chemical and biological systems is to use path-integral molecular dynamics. Unfortunately, conventional path-integral simulations can have an exceedingly large computational cost due to the need to employ an excessive number of coupled classical subsystems (beads) for quantitative accuracy. Here, we combine perturbation theory with the Feynman–Kac imaginary-time path integral approach to quantum mechanics and derive an improved non-empirical partition function and estimators to calculate converged quantum observables. Our perturbed path-integral (PPI) method requires the same ingredients as the conventional approach, but increases the accuracy and efficiency of path integral simulations by an order of magnitude. Results are presented for the thermodynamics of fundamental model systems, an empirical water model containing 256 water molecules within periodic boundary conditions, and ab initio simulations of nitrogen and benzene molecules. For all of these examples, PPI simulations with 4 to 8 classical beads recover the nuclear quantum contribution to the total energy and heat capacity at room temperature within a 3% accuracy, paving the way toward seamless modeling of nuclear quantum effects in realistic molecules and materials.

Graphical abstract: Modeling quantum nuclei with perturbed path integral molecular dynamics

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Supplementary files

Article information


Submitted
12 Sep 2015
Accepted
28 Oct 2015
First published
30 Oct 2015

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2016,7, 1368-1372
Article type
Edge Article
Author version available

Modeling quantum nuclei with perturbed path integral molecular dynamics

I. Poltavsky and A. Tkatchenko, Chem. Sci., 2016, 7, 1368
DOI: 10.1039/C5SC03443D

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