Electronic, magnetic and structural properties of neutral, cationic and anionic Fe₂S₂, Fe₃S₄and Fe₄S₄clusters

Abstract

This work reports density functional calculations of geometric, electronic and magnetic properties of freestanding iron-sulfur Fe 2 S 2 , Fe 3 S 4 and Fe 4 S 4 clusters which are the ones most frequently contained in proteins. We investigate neutral, anionic and cationic clusters using a method that employs linear combinations of atomic orbitals as basis sets, nonlocal norm-conserving pseudopotentials and a generalized gradient approximation to exchange and correlation. The results are discussed in connection with available experimental data. We mainly show that the ground-state geometries of these free clusters are consistent with their structures in core proteins and they are the same in the neutral, anionic and cationic states, but with small distortions. In all cases, an antiferromagnetic order between Fe atoms is always preferred to ferromagnetic and paramagnetic ones. The geometric distortions induced by magnetism decrease with cluster size and the maximum deviation between Fe-Fe distances is 11% in Fe 2 S 2 , but only 4% in Fe 3 S 4 and 3% in Fe 4 S 4 clusters.

Systematic theoretical investigation of geometries, stabilities and magnetic properties of iron oxide clusters (FeO)nμ(n = 1–8, μ = 0, ±1): insights and perspectives

“…The present calculations indicate that within each size, the Fe atom tends to form the largest probable number of bonds with O atoms, which is similar to iron sulfur clusters. 50 As discussed above, we nd that the ground state structures of (FeO) n 0/À/+ clusters are "ring structures" when n # 3, which is similar to the previous reported Fe n O m clusters. 51 When n $ 4, the ground state structures of (FeO) n 0/À/+ exhibit layer-like 3D congurations.…”

Structural and Electronic Rearrangements in Fe2S2, Fe3S4, and Fe4S4 Atomic Clusters under the Attack of NO, CO, and O2

“…The sulfur atom linking the three equivalent iron atoms is substantially polarized (0.35 μ B ), whereas the other three are less (3 × 0.13 μ B ). In our previous work, 18 using SIESTA, 40,41 we found a similar atomic structure with a different antiparallel spin arrangement (singlet state). This singlet state results at 0.18 eV from the ground state in the VASP calculation.…”

“…As reported above, by using the SIESTA code 40,41 that employs Troullier−Martins pseudopotentials instead of PAWs for the core interactions and numerical pseudoatomic orbitals instead of plane waves as basis sets, our group found that these clusters conserve essentially the geometries they have inside core proteins. 18 To have the references of the host clusters, we reoptimized those structures with VASP. The cubic supercell throughout the calculations is chosen with an edge of 15 Å, being large enough to suppress any interaction between the periodically repeated images of the clusters.…”

“…7,16−20 In a previous study, based on density functional theory (DFT), 18 our group found that those freestanding clusters conserve the geometries they have inside core proteins, apart from small distortions. 18 Compared to experimental data in proteins, the bond length of a geometry-optimized structure for the Fe 3 S 4 cluster is compressed within ∼2−5%. The aim of the present work is to carry out a systematical theoretical study of the structural, electronic, and magnetic properties of Fe 2 S 2 , Fe 3 S 4 , and Fe 4 S 4 clusters attacked by NO, CO, and O 2 molecules, which are known to alter the functions of proteins.…”

Evolution of the structure and electronic properties of neutral and anion (n=1–7, μ=0, −1) clusters: A comprehensive analysis

“…For the larger Fe-S clusters, as far as we known, there are few studies. Only the computational study on Fe 2 S clusters [33] have been performed, and the preliminary study on FeS À n (n = 1-6) [13] was carried out. In multicenter clusters, the electrons of iron atoms exhibit a weak magnetic coupling.…”