Efficient treatment of molecular excitations in the liquid phase environment via stochastic many-body theory

Abstract

Accurate predictions of charge excitation energies of molecules in the disordered condensed phase are central to the chemical reactivity, stability, and optoelectronic properties of molecules and critically depend on the specific environment. Herein, we develop a stochastic GW method for calculating these charge excitation energies. The approach employs maximally localized electronic states to define the electronic subspace of a molecule and the rest of the system, both of which are randomly sampled. We test the method on three solute–solvent systems: phenol, thymine, and phenylalanine in water. The results are in excellent agreement with the previous high-level calculations and available experimental data. The stochastic calculations for supercells containing up to 1000 electrons representing the solvated systems are inexpensive and require [Formula: see text] central processing unit hrs. We find that the coupling with the environment accounts for [Formula: see text] of the total correlation energy. The solvent-to-solute feedback mechanism incorporated in the molecular correlation term causes up to 0.6 eV destabilization of the quasiparticle energy. Simulated photo-emission spectra exhibit red shifts, state-degeneracy lifting, and lifetime shortening. Our method provides an efficient approach for an accurate study of excitations of large molecules in realistic condensed phase environments.

Reduced Scaling of Optimal Regional Orbital Localization via Sequential Exhaustion of the Single-Particle Space

“…Previously, we introduced a modified form of the PM functional to account for selected atoms only and search for the N rl states directly. 6 Such a modification is equivalent to the search of a local maximum of on the selected atoms, and it reduces the dimensionality to . In this work, we further compress the to simply 1 by creating a single fragment from the subset of atoms.…”

“…This is quite limiting when nanoscale systems are considered: the dimensionality of matrix Q and the computational scaling make it challenging to work with thousands of electrons. Previously, we introduced a modified form of the PM functional to account for selected atoms only and search for the N rl states directly . Such a modification is equivalent to the search of a local maximum of on the selected atoms, and it reduces the dimensionality to .…”

“…More importantly, they allow the evaluation of nonlocal two-body interaction integrals at a significantly reduced cost due to the reduced spatial overlaps. Hence, they represent a powerful tool in mean-field and postmean-field electronic structure calculations such as hybrid functional calculations, , density functional theory with the Hubbard correction term, , or many-body calculations. , In the same vein, the maximally localized orbital descriptions are optimal for treating correlation phenomena since (due to the locality) the number of “inter-site” interactions is minimal, and the effective size of the problem is smaller. As a result, optimally localized states are essential in the context of embedding and downfolding for many-electron problems. − …”

Reduced scaling of optimal regional orbital localization via sequential exhaustion of the single-particle space

“…This is quite limiting when nanoscale systems are considered: the dimensionality of matrix Q and the computational scaling make it challenging to work with thousands of electrons. Previously, we introduced a modified form of the PM functional to account for N A (N A N A ) selected atoms only and search for the N rl states directly 6 . Such a modification is equivalent to the search of a local maximum of P on the selected atoms, and it reduces the dimensionality to N A × N 2 s .…”

“…Hence, they represent a powerful tool in mean-field and post-mean-field electronic structure calculations such as hybrid functional calculations, 1,2 density functional theory with the Hubbard correction term, 3,4 or many-body caluations. 5,6 In the same vein, the maximally localized orbital descriptions is optimal for treating correlation phenomena since (due to the locality) the number of "inter-site" interactions is minimal, and the effective size of the problem is smaller. As a result, optimally localized states are essential in the context of embedding and downfolding for many-electron problems.…”