A density matrix renormalization group method study of optical properties of porphines and metalloporphines

Abstract

The symmetrized density matrix renormalization group method is used to study linear and nonlinear optical properties of free base porphine and metalloporphine. Long-range interacting model, namely, Pariser-Parr-Pople model is employed to capture the quantum many-body effect in these systems. The nonlinear optical coefficients are computed within the correction vector method. The computed singlet and triplet low-lying excited state energies and their charge densities are in excellent agreement with experimental as well as many other theoretical results. The rearrangement of the charge density at carbon and nitrogen sites, on excitation, is discussed. From our bond order calculation, we conclude that porphine is well described by the 18-annulenic structure in the ground state and the molecule expands upon excitation. We have modeled the regular metalloporphine by taking an effective electric field due to the metal ion and computed the excitation spectrum. Metalloporphines have D(4h) symmetry and hence have more degenerate excited states. The ground state of metalloporphines shows 20-annulenic structure, as the charge on the metal ion increases. The linear polarizability seems to increase with the charge initially and then saturates. The same trend is observed in third order polarizability coefficients.

Density matrix renormalization group algorithm for Bethe lattices of spin-12or spin-1 sites with Heisenberg antiferromagnetic exchange

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Many-Body Effects in FeN4 Center Embedded in Graphene

“…Exact numerical methods are used to account for the many-body physics introduced by the central atom, which we model as a multi-orbital Anderson-like impurity. Generalized Anderson impurity models have been applied previously to porphyrin-like molecules [32,34,37,38,74,75] to predict potential energy surfaces and electronic coupling factors [63,76] for various transition-metal complexes. The advantages of our model Hamiltonian approach are that in this way, we can account for the many-body correlation effects in a numerically exact way, and also, the computations can be scaled relatively easily to handle systems with multiple impurities and more complex geometries.…”

Many-body effects in porphyrin-like transition metal complexes embedded in graphene

“…In this work we construct the organic backbone of the molecule under consideration using an LCAO (or tight-binding) Hamiltonian, while using exact numerical methods to account for all the manybody physics introduced by the central atom, which we model as a multi-orbital Anderson-like impurity. Generalized Anderson impurity models have already been applied to porphyrin-like molecules 32,34,37,38,72,73 and have been able to predict potential energy surfaces and electronic coupling factors 60,74 of different transition metal 51 , this corresponds to five-coordinated iron. The difference between the π and z 2 orbitals is small and has been reversed to match the occupation of the orbitals according to DFT calculations.…”