Structural, electronic and magnetic properties of Pn+1 and FePn (n = 1–14) clusters (original) (raw)
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Embrittlement is known to be caused by P segregation at grain boundaries in Fe alloys. Effects of P substitutions on binding energies and electronic structures of octahedral Fe cluster are investigated using density functional calculations in order to understand the nature of bonding between P and Fe atoms at grain boundaries. The binding energies increase in Fe 3 P 3 and Fe-rich clusters while they decrease in P-rich clusters. The changes in binding energies are closely connected to the charge transfer from Fe to P atoms. The charge transfer leads to both stronger and weaker bonds in mixed Fe-P clusters. The weaker bonds due to less charge cause embrittlement. The calculations indicate that the binding energies and chemical bonding are affected by atomic configurations of P atoms in Fe-P clusters.
Pragya Darshan प्रज्ञा दर्शन, 2023
This work presents a systematic study of the geometric, electronic and magnetic properties of Pd clusters pristine and mono-and bidoped with Mn: Pdn, Pdn−1Mn, Pdn−2Mn 2 where n ≤13. We have used the density functional formalism with the spin polarized generalized gradient approximation. From the variety of possible structures with thirteen atoms, we found the icosahedral configuration to be the most stable as compared to the hexagonal, cub-octahedral and buckled bi-planar. The change in magnetic behavior of Pd clusters after doping with Mn has been observed. This communication is an attempt to understand that behaviour.
Magnetic properties of small Pt-capped Fe, Co, and Ni clusters: A density functional theory study
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Theoretical studies on M 13 (M = Fe, Co, Ni) and M 13 Pt n (for n = 3, 4, 5, 20) clusters including the spin-orbit coupling are done using density functional theory. The magnetic anisotropy energy (MAE) along with the spin and orbital moments are calculated for M 13 icosahedral clusters. The angle-dependent energy differences are modelled using an extended classical Heisenberg model with local anisotropies. From our studies, the MAE for Jahn-Teller distorted Fe 13 , Mackay distorted Fe 13 and nearly undistorted Co 13 clusters are found to be 322, 60 and 5 µeV/atom, respectively, and are large relative to the corresponding bulk values, (which are 1.4 and 1.3 µeV/atom for bcc Fe and fcc Co, respectively.) However, for Ni 13 (which practically does not show relaxation tendencies), the calculated value of MAE is found to be 0.64 µeV/atom, which is approximately four times smaller compared to the bulk fcc Ni (2.7 µeV/atom). In addition, MAE of the capped cluster (Fe 13 Pt 4 ) is enhanced compared to the uncapped Jahn-Teller distorted Fe 13 cluster.
Studies of FemIrn nano clusters using Density Functional Theory Techniques
The structure, binding energy, magnetic moments and electronic structure of FemIrn clusters are investigated using state of the art density functional theory techniques. Fully unconstrained structural relaxations are undertaken by considering all possible non equivalent cluster structures. The optimized clusters are all compact, indicating a clear tendency to maximize the number of nearest neighbour Fe-Ir pairs. The binding energy shows an increment with cluster size. All the clusters preserve ferromagnetic order after optimization. The average magnetic moment generally shows an increase with Fe concentration. The spin polarized density of states is largely dominated by the contribution of d orbitals. An important enhancement of the local Fe moments in an Ir rich environment is observed due to the charge transfer between Fe and Ir. On the other hand, the Ir moments are already large in the pure Ir clusters and does not show significant enhancement with Fe doping. The HOMO-LUMO gaps ...
First principles studies of FemIrn (2 £ m + n £ 4) nano clusters
The structure, binding energy, magnetic moments, and electronic structure of Fe m Ir n (2 B m ? n B 4) nano clusters are investigated using first principles density functional theory techniques. Fully unconstrained structural relaxations are undertaken by considering all possible non-equivalent cluster structures. The optimized clusters are all compact, indicating a clear tendency to maximize the number of nearest neighbor Fe-Ir pairs. The binding energy shows an increment with cluster size. All the clusters preserve ferromagnetic order after optimization and the average magnetic moment shows a general increment with Fe concentration. An enhancement of the local Fe moments in Ir-rich environment is observed, while that of Ir is minimal. The highest occupied molecular orbitallowest unoccupied molecular orbital energy gaps show a general reduction with alloying, indicating more metallicity for the doped clusters than the pure ones.
Chemistry-a European Journal, 2008
We present a theoretical study of the energetic and thermodynamic stability of selected phosphorus and arsenic clusters containing 18 to 168 atoms. For this purpose we employ MP2 as well as DFT functionals BP86 and B3LYP with extended basis sets. All procedures predict the family of one-dimensional polymers X18+12n, each with 2n−1 isomers of virtually identical energy, to be more stable than other structures investigated so far. Furthermore, islands of stability result for ring-shaped clusters X24n with Dnd symmetry for n=4 (only for arsenic), 5, 6, and 7. Phosphorus and arsenic show otherwise a very similar behavior. An investigation of basis set effects shows that a doubly polarized triple zeta valence basis (TZVPP) is both necessary and sufficient. In comparison to the reliable spin component scaled MP2 (SCS-MP2) procedure, DFT methods underestimate and MP2 overestimates the stability of larger clusters; the discrepancy increases with the number of atoms. The addition of a long-range dispersion correction to B3LYP energies does not rectify the shortcomings of DFT in comparison with SCS-MP2.
The Journal of Physical Chemistry A, 2014
In general, because of the high computational demand, most theoretical studies addressing cationic and anionic clusters assume structural relaxation from the ground state neutral geometries. Such approach has its limits as some clusters could undergo a drastic structural deformation upon gaining or losing one electron. By engaging symmetry-unrestricted density functional calculations with an extensive search among various structures for each size and state of charge, we addressed the investigation of the technologically relevant Cu n and Pt n clusters for n = 2−14 atoms in the cationic, neutral, and anionic states to analyze the behavior of the structural, electronic, and energetic properties as a function of size and charge state. Moreover, we considered potentially high-energy isomers allowing foresight comparison with experimental results. Considering fixed cluster sizes, we found that distinct charge states lead to different structural geometries, revealing a clear tendency of decreasing average coordination as the electron density is increased. This behavior prompts significant changes in all considered properties, namely, energy gaps between occupied and unoccupied states, magnetic moment, detachment energy, ionization potential, center of gravity and "bandwidth" of occupied d-states, stability function, binding energy, electric dipole moment and sd hybridization. Furthermore, we identified a strong correlation between magic Pt clusters with peaks in sd hybridization index, allowing us to conclude that sd hybridization is one of the mechanisms for stabilization for Pt n clusters. Our results form a well-established basis upon which a deeper understanding of the stability and reactivity of metal clusters can be built, as well as the possibility to tune and exploit cluster properties as a function of size and charge.
Journal of the American Chemical Society, 1995
Based on self-assembly of the dissymmetrical mononuclear entity CuL(CH 3 OH) [H 2 L = (E)-N 1-(2-((2-aminocyclohexydiimino)(phenyl)methyl)-4-chlorophenyl)-N 2-(2-benzyl-4-chlorophenyl)oxalamide] with Mn(II), two trinuclear complexes were prepared. They are of the formula [(LCuN 3) 2 Mn(CH 3 OH) 2 ] AE 2CH 3 OH AE 2H 2 O (1) and [(LCuSCN) 2 Mn(H 2 O) 2 ] AE 4CH 3 OH (2). Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = À14.40 cm À1 for 1 and J = À15.48 cm À1 for 2. Hydrogen bonds help complex 1 to produce a novel S type one-dimensional chain-like supramolecular structure. In complex 2, ClÁ Á ÁCl interaction also results in the formation of a one-dimensional structure.
Russian Journal of Physical Chemistry A, 2022
The structure, stability, electronic and magnetic properties of 13-, 33-and 55-atom Pd, Pt monometallic and bimetallic core-shell nanoparticles (BCSNPs) were investigated using the density functional theory calculations. The results showed that Pt@Pd BCSNPs with a Pd surface-shell are thermodynamically more favorable than Pd@ Pt with a Pt surface-shell. Interestingly, 33-atom three-shell Pd@Pt 12 @Pd 20 was more stable than two-shell Pt 13 @Pd 20 , while two-shell Pd 13 @Pt 20 was more stable than three-shell Pt@Pd 12 @Pt 20. 55-atom three-shell Pd@ Pt 12 @Pd 42 and Pt@Pd 12 @Pt 42 were more stable than two-shell Pt 13 @Pd 42 and Pd 13 @Pt 42. The Pd@Pt BCSNPs with Pt surface-shell exhibited a negative charge, d-band-center upshift and high chemical activity, while the Pt@Pd BCSNPs with Pd surface-shell displayed a positive charge, d-band center downshift and low chemical activity. 13-and 55-atom NPs with Pd surface-shell displayed higher total magnetic moment than those with Pt surface-shell except Pd 13 @Pt 20. 33-atom NPs with Pt surface-shell afforded higher total magnetic moment than those with Pd surface-shell.
The European Physical Journal D, 2009
Here we report a systematic theoretical study of the structure and electronic properties of Snn−1Pb and Pbn−1Sn (n = 2−13) clusters and compare these results with pure Snn and Pbn to understand the influence of the dopant elements. The calculations were carried out using the density functional theory with generalized gradient approximation for the exchange-correlation potential. Extensive search based on large number of initial configurations has been carried out to locate the stable isomers of Snn−1Pb and Pbn−1Sn (n = 2−13) clusters. The relative stability of Snn−1Pb and Pbn−1Sn (n = 2−13) clusters is analyzed based on the calculated binding energies and second difference in energy. The stability analysis of these clusters suggests that, while the substitution of Sn by Pb lowers the stability of Snn clusters, presence of Sn enhances the stability of the Pbn clusters. The results suggest that while for Snn−1Pb, n = 4, 7, 10, 12 clusters are more stable than their respective neighbors, Pbn−1Sn clusters with n = 4, 7 and 9 are found to be more stable. Based on the fragmentation pattern it is seen that for Snn−1Pb and Pbn−1Sn clusters favor monomer evaporation of the Pb atom up to n = 11 and n = 12, respectively. Unlike this trend, the Sn11Pb undergoes fission type fragment into Sn5Pb and Sn6 clusters. A comparison between our theoretical results and surface induced dissociation experiment shows good agreement, which gives confidence on the prediction of the ground state geometries.