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Updated: Jul 10, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Published on: December 4, 2017

Quantum mechanical correlation functions, maximum entropy analytic continuation, and ring polymer molecular dynamics.

Scott Habershon¹, Bastiaan J Braams, David E Manolopoulos

¹Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom.

The Journal of Chemical Physics

|November 13, 2007

Summary

This summary is machine-generated.

Combining maximum entropy analytic continuation (MEAC) and ring polymer molecular dynamics (RPMD) offers a superior method for calculating quantum correlation functions. This hybrid approach improves accuracy, especially for short-time dynamics, by leveraging the strengths of both techniques.

Related Experiment Videos

Last Updated: Jul 10, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Published on: December 4, 2017

Area of Science:

Quantum chemistry
Computational physics
Statistical mechanics

Background:

Ring polymer molecular dynamics (RPMD) is accurate at high temperatures.
Maximum entropy analytic continuation (MEAC) excels at low temperatures.
Both methods calculate real-time quantum correlation functions.

Purpose of the Study:

To combine MEAC and RPMD for improved quantum correlation function calculations.
To address limitations of individual methods.
To provide a more accurate approximation than either method alone.

Main Methods:

Utilizing the complementary temperature regimes of MEAC and RPMD.
Applying MEAC to impose exact moment constraints on RPMD spectra.
Calculating imaginary-time correlation functions concurrently with RPMD.

Main Results:

The combined RPMD+MEAC method offers improved accuracy over individual approaches.
This hybrid method effectively solves the RPMD "nonlinear operator problem".
Good agreement was achieved with exact results for liquid parahydrogen's velocity autocorrelation function.

Conclusions:

The combined MEAC and RPMD approach provides a practical and efficient enhancement for quantum dynamics calculations.
This method is particularly effective for short-time dynamics.
Long-time dynamics remain a challenge for the combined method, as seen in liquid orthodeuterium simulations.