Quantum dynamics using path integral coarse-graining

The vibrational spectra of condensed and gas-phase systems are influenced by thequantum-mechanical behavior of light nuclei. Full-dimensional simulations of approximate quantum dynamics are possible thanks to the imaginary time path-integral (PI) formulation of quantum statistical mechanics, albeit at a high computational cost which increases sharply with decreasing temperature. By leveraging advances in machine-learned coarse-graining, we develop a PI method with the reduced computational cost of a classical simulation. We also propose a simple temperature elevation scheme to significantly attenuate the artifacts of standard PI approaches as well as eliminate the unfavorable temperature scaling of the computational cost. We illustrate the approach, by calculating vibrational spectra using standard models of water molecules and bulk water, demonstrating significant computational savings and dramatically improved accuracy compared to more expensive reference approaches. Our simple, efficient, and accurate method has prospects for routine calculations of vibrational spectra for a wide range of molecular systems - with an explicit treatment of the quantum nature of nuclei.

Automated summary

This research develops a method for accurately calculating vibrational spectra of molecular systems using a reduced computational cost path-integral formulation. By leveraging advances in machine-learned coarse-graining and a simple temperature elevation scheme, significant computational savings and improved accuracy are achieved compared to more expensive reference approaches. This method has the potential for routine calculations of vibrational spectra for a wide range of molecular systems with an explicit treatment of the quantum nature of nuclei.