Efficient Treatment of Molecular Excitations in the Liquid phase using stochastic many-body theory

I will present an efficient method to compute charge excitation in structurally inhomogeneous and disordered systems based on stochastic formulation of many-body perturbation theory. Our approach effectively separates the problem into separate subspaces corresponding to a molecule and the environment, and yields reconstructed molecular states. The electronic correlations are stochastically sampled in each subspace and can treat giant systems with thousands of electrons. I will exemplify the method on molecular quasiparticle energies in the liquid environment, representing systems of wide interest. Our method is first tested on three solute-solvent systems: phenol, thymine, and phenylalanine in water. Our computed results are in excellent agreements with photoemission experiments and the resulting environmental effects are on par with high-level quantum chemistry calculations. I will comment on the interactions between molecule and the environment: the screening of the environment accounts for $\sim40\%$ of the correlation energy, while secondary solute-solvent feedback can also cause up to 0.6 eV destabilization of the quasiparticle energy. Our method is further applied to molecules in non-aqueous solvents and the calculated solvent effects are analyzed upon their electric polarizability.