Electron correlation in the Iron(II) Porphyrin by NOF approximations

Abstract

The relative stability of the singlet, triplet, and quintet spin states of Iron(II) porphyrin (FeP) represents a challenging problem for electronic structure methods. While it is currently accepted that the ground state is a triplet, multiconfigurational wavefunction-based methods predict a quintet, and density functional approximations vary between triplet and quintet states, leading to a prediction that highly depends on the features of the method employed. The recently proposed Global Natural Orbital Functional (GNOF) aims to provide a balanced treatment between static and dynamic correlation, and together with the previous Piris Natural Orbital Functionals (PNOFs), allowed us to explore the importance of each type of correlation in the stability order of the states of FeP with a method that conserves the spin of the system. It is noteworthy that GNOF correlates all electrons in all available orbitals for a given basis set; in the case of the FeP with a double zeta basis set as used in this work; this means that GNOF can properly correlate 186 electrons in 465 orbitals, significantly increasing the sizes of systems amenable to multiconfigurational treatment. Results show that PNOF5, PNOF7s and PNOF7 predict the quintet to have a lower energy than the triplet state; however, the addition of dynamic correlation via second-order Moller-Plesset corrections (NOF-MP2) turns the triplet state to be lower than the quintet state, a prediction also reproduced by GNOF that incorporates much more dynamic correlation than its predecessors.

arXiv comment17 pages, 5 Tables, 1 Figure

References in corpus (29)

• Cheap and near exact CASSCF with large active spaces
• Global Method for Electron Correlation
• Understanding the mechanism stabilizing intermediate spin states in Fe(II)-Porphyrin
• Global Natural Orbital Functional: Towards the Complete Description of the Electron Correlation
• Diverging exchange force and form of the exact density matrix functional
• Ensemble reduced density matrix functional theory for excited states and hierarchical generalization of Pauli's exclusion principle
• Utilizing Essential Symmetry Breaking in Auxiliary-Field Quantum Monte Carlo: Application to the Spin Gaps of the C${}_{36}$ Fullerene and an Iron Porphyrin Model Complex
• Reduced Density-Matrix Approach to Strong Matter-Photon Interaction
• Foundation of one-particle reduced density matrix functional theory for excited states
• DoNOF: an open-source implementation of natural-orbital-functional-based methods for quantum chemistry
• The dynamic electron-correlation energy in the NOF-MP2 method from the orbital-invariant perturbation theory
• Natural orbital functional for multiplets
• Reduced Density Matrix Functional Theory for Bosons
• Phase Dilemma in Natural Orbital Functional Theory from the N-representability Perspective
• One-body reduced density-matrix functional theory in finite basis sets at elevated temperatures
• Reduced Density Matrix Functional Theory for Superconductors
• Benchmarking GNOF against FCI in challenging systems in one, two and three dimensions
• An efficient method for strongly correlated electrons in two-dimensions
• An efficient method for strongly correlated electrons in one dimension
• Ground State of the Fe(II)-porphyrin Model System Corresponds to the Quintet State: A DFT and DMRG-based Tailored CC Study
• Towards a Resolution of the Static Correlation Problem in Density Functional Theory from Semidefinite Programming
• Introducing screening in one-body density matrix functionals: impact on the Extended Koopmans' Theorem's charged excitations of model systems
• Reduced density matrix functional theory from an ab initio seniority-zero wave function: Exact and approximate formulations along adiabatic connection paths
• On the time evolution of fermionic occupation numbers
• Analytic gradients for spin multiplets in natural orbital functional theory
• Implications of the unitary invariance and symmetry restrictions on the development of proper approximate one-body reduced density matrix functionals
• Functional Theory for Bose-Einstein Condensates
• Performance of the NOF-MP2 method in hydrogen abstraction reactions
• Natural orbital functional for spin-polarized periodic systems

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