Field-Theory Approach to Molecular Interactions

The quantum-mechanical theory of molecular interactions is firmly established, however its applicability to large molecular complexes is hindered by the rather high computational cost of quantum calculations required to achieve high accuracy. We propose a paradigm shift in the modeling and conceptual understanding of electrostatic and electrodynamic molecular interactions in many-particle systems from the perspective of (quantum) field theory. This development is critical to accurately and efficiently model increasingly intricate and functional molecular ensembles with millions of atoms subject to external excitations (static, thermal, and optical fields; variation in the number of particles; and/or arbitrary macroscopic boundary conditions). This molecular size covers a wide range of functional biological systems, including solvated protein/protein and enzyme/DNA complexes. The theoretical developments in this project will concentrate on two main fronts: (WP1) fundamental quantum electrodynamics (QED) theory of molecular interactions based on many-body oscillator Hamiltonians, (WP2) second-quantized field theory (FIT) approach to molecular Hamiltonians for modeling large-scale systems with 10^4-10^6 atoms. The applicability of these challenging developments to realistic molecules will be ensured by: (WP3) implementation of non-local machine learning force fields based on second-quantized matrix Hamiltonians for efficient molecular dynamics simulations of molecular ensembles, (WP4) implementation of QED/FIT methods in an open-source package FITMOL for increasing the accuracy, improving the efficiency, and enhancing the insight that one obtains from quantum-mechanical calculations of large molecules. It is my vision that revealing fundamental mechanisms of functional (bio)molecules with millions of atoms requires a radically new field-theory approach to molecular interactions. Achieving this goal will be the main breakthrough of the FITMOL project.