Simulation of heme using DFT + U:  a step toward accurate spin-state energetics

• Autores: Scherlis Perel, Damian Ariel; Cococcioni, Matteo; Sit, Patrick; Marzari, Nicola
• Año de publicación: 2007
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: SPIN STATES; DFT+U; IRON; BIOINORGANIC CHEMISTRY; PYRROLES; PORPHYRINS; LIGANDS
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We investigate the DFT + U approach as a viable solution to describe the low-lying states of ligated and unligated iron heme complexes. Besides their central role in organometallic chemistry, these compounds represent a paradigmatic case where LDA, GGA, and common hybrid functionals fail to reproduce the experimental magnetic splittings. In particular, the imidazole pentacoordinated heme is incorrectly described as a triplet by all usual DFT flavors. In this study, we show that a U parameter close to 4 eV leads to spin transitions and molecular geometries in quantitative agreement with experiments and that DFT + U represents an appealing tool in the description of iron porphyrin complexes, at a much reduced cost compared to correlated quantum-chemistry methods. The possibility of obtaining the U parameter from first principles is explored through a self-consistent linear-response formulation. We find that this approach, which proved to be successful in other iron systems, produces in this case some overestimation with respect to the optimal values of U.
Fil: Scherlis Perel, Damian Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina
Fil: Cococcioni, Matteo. University of Minnesota; Estados Unidos
Fil: Sit, Patrick. Massachusetts Institute of Technology; Estados Unidos
Fil: Marzari, Nicola. Massachusetts Institute of Technology; Estados Unidos