Obtaining the magnetic susceptibility of the heme complex from DFT calculations

• Published in: AIP advances 2016-09, Vol.6 (9), p.095105-095105-10
• Main Authors: Pereira, L. M. O., Resende, S. M., Leite Alves, H. W.
• Format: Article
• Language: English
• Subjects: Accuracy; Density functional theory; Electronic structure; Histidine; Iron; Ligands; Magnetic permeability; Magnetic properties; Magnetism; Quantum mechanics
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.4962663

Magnetic field interactions with particles, as observed in magnetophoresis, are becoming important tool to understand the nature of the iron role in heme molecular complex, besides other useful applications. Accurate estimations of some macroscopic magnetic properties from quantum mechanical calculations, such as the magnetic susceptibility, can also check the reliability of the heme microscopic models. In this work we report, by using the Stoner criterion, a simple way to obtain the magnetic susceptibility of the heme complex from Density Functional Theory calculations. Some of our calculated structural properties and electronic structure show good agreement with both the available experimental and theoretical data, and the results show that its groundstate is a triplet 3A state. From the obtained results, we have evaluated the exchange interaction energy, J = 0.98 eV, the associated magnetic energy gain, Δ E M = − 0.68 eV, and the magnetic susceptibility, χ 0 = 1.73 × 10 − 6 cm3/mol for the heme alone (with uncompleted Fe ligands). If we consider the heme complex with the two histidine residues (completing the Fe ligands), we have then obtained χ 0 = 5.27 × 10 − 12 cm3/g, which is in good agreement with experimental magnetophoresis data.