Superexchange mechanism and quantum many body excitations in the archetypal di-Cu oxo-bridge

Abstract

We perform first-principles quantum mechanical studies of dioxygen ligand binding to the hemocyanin protein. Electronic correlation effects in the functional site of hemocyanin are investigated using a state-of-the-art approach, treating the localised copper 3d electrons with cluster dynamical mean field theory (DMFT) for the first time. This approach has enabled us to account for dynamical and multi-reference quantum mechanics, capturing valence and spin fluctuations of the 3d electrons. Our approach explains the stabilisation of the experimentally observed di-Cu singlet for the butterflied Cu 2 O 2 core, with localised charge and incoherent scattering processes across the oxo-bridge that prevent long-lived charge excitations, suggesting that the magnetic structure of hemocyanin is largely influenced by the many-body corrections. Our computational model is supported by agreement with experimental optical absorption data, and provides a revised understanding of the bonding of the peroxide to the di-Cu system in vivo.

The ONETEP linear-scaling density functional theory program

“…ONETEP + TOSCAM has already been used to explain the insulating M 1 phase of vanadium dioxide, 104 to demonstrate the importance of Hund's coupling in the binding energetics of myoglobin, 145,146 and to study the superexchange mechanism in the dicopper oxo-bridge of hemocyanin and tyrosinase. 147 C. Dynamics and structure optimization…”

Dimerization in α-TiCl3 and α-TiBr3: the DFT study

“…While such methods as DFT + U strongly overestimate tendency to localize electrons at the atomic sites, more accurate calculation schemes based on the cluster extensions of dynamical mean field theory (as e.g. [20][21][22]) or other quantum embedding approaches [23][24][25] should be used to describe the low temperature phase of both materials. It is essential to consider a whole Ti-Ti cluster as an impurity, since only in this case tendency to form molecular orbitals and strong Coulomb interaction will be treated on equal footing.…”

Superlight pairs in face-centred-cubic extended Hubbard models with strong Coulomb repulsion

“…There are many numerical techniques that are suitable for treating strongly correlated systems, including extended Hubbard models. These include exact diagonalisation (ED) [21], density matrix renormalisation group (DMRG) and matrix product state calculations [22,23], dynamical mean-field theory (DMFT), its extensions dynamical cluster approximation, cellular DMFT, and extended DMFT to treat extended Hubbard models [12,[24][25][26][27], quantum Monte Carlo (QMC) techniques [1], and recently quantum embedding [28][29][30] and machine learning algorithms [31]. Many of these techniques are limited to 1D and 2D systems, either inherently, or because particle numbers are limited.…”