Modeling the Excited States of Biological Chromophores within Many-Body Green’s Function Theory

Abstract

First-principle many-body Green's function theory (MBGFT) has been successfully used to describe electronic excitations in many materials, from bulk crystals to nanoparticles. Here we assess its performance for the calculations of the excited states of biological chromophores. MBGFT is based on a set of Green's function equations, whose key ingredients are the electron's self-energy Σ, which is obtained by Hedin's GW approach, and the electron-hole interaction, which is described by the Bethe-Salpeter equation (BSE). The GW approach and the BSE predict orbital energies and excitation energies with high accuracy, respectively. We have calculated the low-lying excited states of a series of model biological chromophores, related to the photoactive yellow protein (PYP), rhodopsin, and the green fluorescent protein (GFP), obtaining a very good agreement with the available experimental and accurate theoretical data; the order of the excited states is also correctly predicted. MBGFT bridges the gap between time-dependent density functional theory and high-level quantum chemistry methods, combining the efficiency of the former with the accuracy of the latter: this makes MBGFT a promising method for studying excitations in complex biological systems.

Short-Range to Long-Range Charge-Transfer Excitations in the Zincbacteriochlorin-Bacteriochlorin Complex: A Bethe-Salpeter Study

“…Consistently with previous observations, 28,44 we find that the diagonalization of the full BSE Hamiltonian leads to a red shift which can be as large as 0.35 eV as compared to the GW -BSE results in the TammDamcov (TDA) approximation, bringing the calculated transitions in excellent agreement with experiment. Such a good agreement with available experimental data can be taken as an indication of the reliability of the present formalism and of the specific implementation aspects.…”

“…Such a basis derives from previous studies [27][28][29] but with additional diffuse orbitals. The needed starting single-particle states are taken to be the Kohn-Sham DFT/LDA eigenstates generated by the Siesta package 30 using a large triple-zeta plus double polarization basis (TZDP).…”

Excited states properties of organic molecules: from density functional theory to the GW and Bethe–Salpeter Green's function formalisms

“…Three independent ab initio implementations were developed simultaneously in 1998 [82][83][84]. Because BSE calculations require as an input the GW quasi-particle energy levels, 4 'GW-BSE' calculations on molecular systems such as fullerenes or porphyrins have also emerged rather recently [88][89][90][91][92][93][94][95][96][97][98], after pioneering studies on small molecules [99,100] or bulk organic semiconductors [101][102][103].…”

Solvent effects on optical excitations of poly para phenylene ethynylene studied by QM/MM simulations based on many-body Green's functions theory

“…All steps involving the actual GW -BSE calculations are performed using the implementation for isolated systems [23,27,55,56], available in the XTP module of the VOTCA software package [57,58]. In VOTCA, the quantities in the GW self-energy operator (dielectric matrix, exchange and correlation terms) and the electron-hole interaction in the BSE are expressed in terms of auxiliary atom-centered Gaussian basis functions.…”