Theory of magnetic and structural ordering in iron clusters

Abstract

The structural properties of neutral iron clusters Fe"(n~4) are investigated using a first-principles, all-electron, linear-combination-of-Gaussian-orbitals method. The ground states are all ferromagnetic with highest-dimensional geometry. They exhibit a tendency toward enhanced bond length, narrower d-band widths, and maximum pairs of nearest-neighbor bonds. Such conditions are favorable for maximizing the energy gain for ferromagnetism, thereby stabilizing the ground-state geometry.

First principles studies of Fe m Ir n (2 ≤ m + n ≤ 4) nano clusters

“…One observes that the inter atomic distances follow the trends in the atomic radii as in the case of dimers. For Fe 3 , the lowest energy structure is an equilateral triangle with bond length 2.19 Å , in good agreement with previous DFT studies, which have reported bond lengths of 2.15, 2.37, 2.04, 2.10 and 2.11 Å (Chen et al 1991;Gong and Zheng 1995;Castro and Salahub 1994;Oda et al 1998;Ballone and Jones 1995) respectively. Compared to Fe 2 , the bond length shows a tendency to increase, indicating that the system always favors the highest dimension for longer bond length.…”

“…The Fe-Fe bond length, 2.00 Å , is in consistent with the experimental values 1.87 Å (Montano and Shenoy 1980) and 2.02 Å (Purdum et al 1982) obtained in different studies and theoretical results of Gong Appl Nanosci (2014) 4:593-600 595 and Zheng (1995), which has shown a bond length of 2.09 Å . However, the calculated bond length is considerably smaller than the nearest neighbor distance, 2.48 Å in bulk bcc Fe (Kittel 2008 (Chen et al 1991;Oda et al 1998;Ballone and Jones 1995), and is in keeping with the value obtained in experiments (3.3 ± 0.5) (Cox et al 1985). For the pure Fe and Ir dimers, the local and average magnetic moments are equal and it indicates that the spin density,…”

“…Small Fe N clusters are studied both experimentally (Montano et al 1980;Purdum et al 1982;Moskovits and Diella 1980;Cox et al 1985) and theoretically (Chen et al 1991;Castro and Salahub 1994;Oda et al 1998;Ballone and Jones 1995;Chen et al 1991;Yu et al 2007;Dieguez et al 2001) using different techniques, and showed compact structure with enhanced magnetic moments of about 3l B /atom. Studies on small Fe clusters carried out by Chen et al (1991) have shown a ferromagnetic ground state with enhanced magnetic moments and smaller inter-atomic distances compared to the bulk phase. Apart from the clusters of a single element, combinations of transition metals are also studied due to the interesting properties that can arise due to alloying (Munoz-Navia et al 2009).…”

“…Studies on the structural and magnetic properties of small metal clusters are carried out with great interest, both experimentally (Parks et al 1988;Liyanage et al 2003) and theoretically (Chen et al 1991;Gong and Zheng 1995;Ma et al 2007). These studies are important as clusters play an important bridge between the atom and bulk, thus in understanding the transition from small to big.…”

Hydrogenated and deuterated iron clusters: Infrared spectra and density functional calculations

“…DFT calculations are known to describe structural and vibrational properties very accurately. 39,40 Several DFT calculations have been done on bare Fe clusters, including up to seven atoms, [41][42][43][44] but we are not aware of calculations on hydrogenated clusters. For the Fe n H m clusters studied here, precise structures are not known and the size of these clusters prevents an extensive search of cluster configurations using firstprinciples calculations to find the minimum energy structures.…”