Nuclear Quantum Effects in Atomistic Simulations of Nonlinear Vibrational Spectra of Complex System

• Applicant: Dr. Yair Litman
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces ; Theoretical Chemistry: Electronic Structure, Dynamics, Simulation ; Theoretical Condensed Matter Physics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467724959

Vibrational energy transfer is relevant to many areas of science since it plays a prominent role in processes such as chemical reactions, allosteric communication in proteins, and heat transport in materials. The study of vibrational dynamics has greatly benefited from the advances of laser technology in the previous decades which sparked the development of different types of ultrafast nonlinear spectroscopy with impressively high resolution in time and space. However, detailed information can rarely be extracted from experimental results alone and theoretical simulations are often required to interpret the data and obtain atomistic insights. In this project, new algorithms and simulation strategies will be developed to bridge some of the gaps between existing simulation approaches and the increasing amount of novel nonlinear vibrational spectroscopic data available. We will focus on the inclusion of nuclear quantum effects (NQEs), which are known to play a major role in the structural and dynamical properties of systems that contain light nuclei but are often neglected in computational approaches. The developments will be based on the path integral approach to quantum mechanics, since it provides a favorable compromise between accuracy and computational cost, and therefore facilitates the study of high-dimensional realistic systems. In particular, methods that have been employed to decode linear spectra will be considerably extended to allow the computation of several types of nonlinear spectroscopy, including two-dimensional infrared (2D-IR) and two-dimensional sum frequency generation (2D-SFG) spectra.The new methodology will be applied to investigate real-world systems, starting with small molecules, such as methane and water, and building up to the more challenging aqueous condensed phased systems. The research program will conclude with the study of the biologically and technologically relevant water-air interface through the simulation of surface-specific spectroscopic signals. We will be able to simulate for the first time the 2D-SFG spectrum of the water-air interface including NQEs ‒ a key observable for the understanding of the water dynamics at the interface and the elucidation of its different energy transfer mechanisms.The outcome of this research project will represent a significant step towards the improvement of theoretical modeling of vibrational dynamics and the interpretation of multidimensional vibrational spectroscopic data. It is expected to have a considerable impact on our current understanding of quantum effects in vibrational energy transfer in general, and vibrational dynamics in aqueous systems in particular.

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professor Dr. Stuart C. Althorpe