Small iron doped carbon clusters: A comparison with early and late first-row transition metal doped clusters

Abstract

A systematic study of the three lowest-lying structures, namely, linear, fan, and cyclic, of neutral FeC(n) (n = 1-8) clusters on the singlet, triplet, quintet, and septet potential energy surfaces has been carried out. Predictions for their electronic energies, rotational constants, dipole moments, and vibrational frequencies have been made using the B3LYP method in conjunction with the 6-311+G(d) basis set. Triplet or quintet states are found as the lowest-lying ones for FeC(n) clusters, and the septet states are found more stable than the singlet ones. The incremental binding energies show an even-odd parity effect, with n-even clusters being more stable than the n-odd ones in the linear and fan clusters, whereas a decrease with n is found for cyclic ones. The most stable isomers for FeC(n) clusters correspond to a fan-type structure for n < or = 4, whereas for n > or = 6 cyclic structures are the most stable. Only in the case of n = 5 the most stable isomer is the linear structure. Comparing the results of FeC(n) clusters with the previously studied TMC(n) (TM = Sc, Ti, V, Co, and Zn) systems, we can see that, as it should be expected, iron doped carbon clusters present an intermediate behavior between early and late first-row transition metal doped clusters.

Small binary iron‐carbon clusters with persistent high magnetic moments. A theoretical characterization

“…[39][40][41] Several methodologies, most of them within the density functional theory (DFT), have been used for many years to study clusters made of pure iron, [12,[42][43][44] iron oxide, [45][46][47][48] and iron-carbon. [20,21,[49][50][51][52][53][54][55][56][57][58][59][60][61] Recently, Zheng et al [21] did an exhaustive and chronological review of the methodologies used during the last two decades for neutral binary ironcarbon clusters. Accordingly, more than 20 different theoretical methods have been used throughout that time.…”

UV spectra of iron-doped carbon clusters FeCn n=3–6

“…Their electronic spectra were measured between 230 and 300 nm by a mass-resolved 1+1 resonant two-photon ionization technique. Higher-resolution scans of the first strong bands were compared with simulated rotational profiles using ground state structures previously calculated at the B3LYP/6-311+G(d) level [49,51]. Observed and predicted profiles agree reasonably well for a fan structure of FeC 3 .…”

“…However, in comparison with the observed absorption profile of FeC 4 at 287.61 nm, it seems more likely that a non-linear molecule is observed. It should be noted that three non-linear geometries with C 2v or close to C 2v symmetry and with different electronic ground states ( 5 B 1 , 3 A', and 5 A 1 ) are predicted by theory to be within 40 kJ/mol of the linear structure [49,51].…”

“…High-resolution spectra at optical and mm wavelengths were measured only for FeC [30][31][32][33][34][35]. Several small Fe n C m (n < 8, m < 11) species have been the subject of theoretical calculations [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51]. The structures and electronic properties of the small clusters are important to understand the growth mechanism of larger compounds, such as met-cars and nanotubes.…”

“…Conclusions concerning the molecular structures are drawn. The most recent calculations of the ground state geometries of these molecules applied the DFT functional B3LYP in conjunction with the 6-311+G(d) basis set [49,51]. It was found that the minimum energy structure is planar fan-like (C 2v ) for FeC 3 and FeC 4 , linear (C ∞v ) for FeC 5 , and cyclic (C 2v ) for FeC 6 (Fig.…”