Size Dependence Adsorption of Hydrogen on Cobalt Clusters: A DFT Study

2016 ◽  
Vol 42 ◽  
pp. 100-111 ◽  
Author(s):  
Ali Nakhaei Pour ◽  
Javad Karimi ◽  
Zahra Keyvanloo ◽  
Mohamadreza Hashemian
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Metal Cluster ◽  
Volume Ratio ◽  
Functional Theory ◽  
Cobalt Clusters ◽  
Size Dependent ◽  
Dependent Parameter ◽  
Adsorption Of Hydrogen ◽  
Cohesive Energies

Density functional theory was used to investigate the effect of size on the adsorption state of hydrogen atom on small cobalt particles. For this propose, we have performed series of DFT-GGA calculations on various sizes of Co clusters, between 4 and 24 atoms, and a Co FCC (100) slab, with and without hydrogen atom adsorbate. The results showed that the destabilization and the cohesive energies per atom in a metal cluster are represented as linear function of the surface-to-volume ratio of the metal clusters. In addition, the energy of the HOMO–LUMO gap from 4s and 3d valence orbitals of the cobalt atoms in the cluster is decreased with increasing in cobalt cluster size, which is size dependent parameter. We have studied the effect of the size of Co clusters and the infinite Co (100) surface, on the energy of adsorption of hydrogen atom. The calculated Eads for hydrogen atom in our considered cobalt clusters showed decreasing behavior with increasing of the number of atoms in cluster.

DFT Calculations on Group 5 Mixed Metal Tetramers: TaxNbyVz (x + y + z = 4)

2004 ◽  
Vol 57 (12) ◽  
pp. 1197 ◽  
Author(s):  
Magdalene A. Addicoat ◽  
Mark A. Buntine ◽  
Gregory F. Metha
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Triplet State ◽  
Density Functional ◽  
Metal Cluster ◽  
Functional Theory ◽  
Mixed Metal ◽  
Mixed Metal Cluster ◽  
Group 5

We report Density Functional Theory (DFT) calculations on mixed-metal tetramers comprised of the Group 5 (Vb) elements V, Nb, and Ta. Our results show that the lowest energy structures for Nb4 and Ta4 are regular tetrahedra with Td symmetry and singlet multiplicity whereas V4 is a triplet state with C2v symmetry. The monosubstituted isomers, A3B, all have C3v symmetry but several higher energy Cs structures have been found that are approximately 100 kJ mol−1 higher in energy. The disubstituted isomers all posses arachno-butterfly structures; the A2B2 types with C2v symmetry and the A2BC types with Cs symmetry. However, the relative openness of the arachno structures is found to be specific to the composition of the mixed-metal cluster.

scholarly journals Isolation of a Bimetallic Cobalt(III) Nitride and Examination of its Hydrogen Atom Abstraction Chemistry and Reactivity Towards H2

2020 ◽  
Author(s):  
Debabrata Sengupta ◽  
Christian Sandoval-Pauker ◽  
Emily Schueller ◽  
Angela M. Encerrado-Manriquez ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Atom Abstraction ◽  
Functional Theory ◽  
Kinetic Rate ◽  
Rate Analysis ◽  
Stable Product ◽  
Activation Pathways ◽  
Computational Analyses

Room temperature photolysis of the bis(azide)cobaltate(II) complex [Na(THF)<sub>x</sub>][(<sup>ket</sup>guan)Co(N3)2] (<sup>ket</sup>guan = [(tBu2CN)C(NDipp)2]–, Dipp = 2,6-diisopropylphenyl) (3a) in THF cleanly forms the binuclear cobalt nitride [Na(THF)4{[(<sup>ket</sup>guan)Co(N3)]2(μ-N)}]<sub>n</sub> (1). Compound 1 represents the first example of an isolable, bimetallic cobalt nitride complex, and it has been fully characterized by spectroscopic, magnetic, and computational analyses. Density functional theory supports a CoIII=N=CoIII canonical form with significant π-bonding between the cobalt centers and the nitride atom. Unlike other Group 9 bridging nitride complexes, no radical character is detected at the bridging N-atom of 1. Indeed, 1 is unreactive towards weak C-H donors and even co-crystallizes with a molecule of cyclohexadiene (CHD) in its crystallographic unit cell to give 1·CHD as a room temperature stable product. Notably, addition of pyridine to 1 or photolyzed solutions of [(<sup>ket</sup>guan)Co(N3)(py)]<sub>2</sub> (4a) leads to destabilization via activation of the nitride unit, resulting in the mixed-valent Co(II)/(III) bridged imido species [(<sup>ket</sup>guan)Co]2(μ-NH)(μ-N3) (5) formed from intermolecular hydrogen atom abstraction (HAA) of strong C-H bonds (BDE ~ 100 kcal/mol). Kinetic rate analysis of the formation of 5 in the presence of C6H12 or C6D12 gives a KIE = 2.5±0.1, supportive of a HAA formation path-way. The reactivity of our system was further probed by photolyzing C6D6/py-d5 solutions of 4a under an H2 atmosphere (150 psi), which leads to the exclusive formation of the bis(imido)[(<sup>ket</sup>guan)Co(μ-NH)]2 (6) as a result of dihydrogen activa-tion. These results provide unique insights into the chemistry and electronic structure of late 3d-metal nitrides while providing entryway into C-H activation pathways.

scholarly journals Effect of BN nanodots on the electronic properties of α- and β-graphyne sheets: a density functional theory study

2019 ◽  
Vol 13 (4) ◽  
pp. 357-364
Author(s):  
R. Majidi ◽  
H. Eftekhari ◽  
H. Bayat ◽  
Kh. Rahmani ◽  
A. M. Khairogli
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Density Functional ◽  
Band Gaps ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Nanoelectronic Devices ◽  
Hexagonal Shape ◽  
Structural And Electronic Properties ◽  
Cohesive Energies

Abstract The effect of BN nanodots with hexagonal shape on the electronic properties of α- and β-graphyne sheets is investigated. The structural and electronic properties of α- and β-graphyne sheets doped with BN nanodots are studied by using density functional theory. The cohesive energies of the systems indicate all considered structures are thermally stable. It is found that hexagonal BN nanodots can effectively open the band gap in α- and β-graphyne sheets. It means BN nanodots change α- and β-graphyne sheets from semimetal to semiconductor. The BN nanodots with different sizes are considered. It is found that band gaps of the studied α- and β-graphyne sheets doped with BN nanodots increase with the increase in the size of BN nanodots. Hence, α- and β-graphyne sheets doped with BN nanodots are promising materials for use in nanoelectronic devices based on semiconductors.

scholarly journals Theoretical Investigation on Structure-Property Relationship of Asymmetric Clusters (CH3FBN3)n (n = 1– 6)

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Deng-Xue Ma ◽  
Yao-Yao Wei ◽  
Yun-Zhi Li ◽  
Guo-Kui Liu ◽  
Qi-Ying Xia
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Dft Method ◽  
Energy Difference ◽  
Structure Property ◽  
Functional Theory ◽  
Size Dependent ◽  
Stable Clusters ◽  
Chemical Inertness ◽  
Relationship Of

The structural, relative stability, electronic, IR vibrational, and thermodynamic properties of asymmetric clusters (CH3FBN3)n (n = 1–6) are systematically investigated using density functional theory (DFT) method. Results show that clusters (CH3FBN3)n (n = 2–6) form a cyclic structure with a B atom and a Nα atom binding together. Five main characteristic regions are observed and assigned for the calculated IR spectra. The size-dependent second-order energy difference shows that clusters (CH3FBN3)3 and (CH3FBN3)5 have relatively higher stability and enhanced chemical inertness compared with the neighboring clusters. These two clusters may serve as the cluster-assembled materials. The variations of thermodynamic properties with temperature T or cluster size n are analyzed, respectively. Based on enthalpies in the range of 200–800 K, the formations of the most stable clusters (CH3FBN3)n (n = 2–6) from monomer are thermodynamically favorable. These data are helpful to design and synthesize other asymmetric boron azides.

Energetics and Structural Investigation of Double-Walled Carbon and Silicon Nanotubes

2000 ◽  
Vol 633 ◽  
Author(s):  
Solange B. Fagan ◽  
Daniela S. Sartor ◽  
R. Mota ◽  
R. J. Baierle ◽  
Antônio J. R. da Silva ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
First Principles ◽  
Density Functional ◽  
Structural Investigation ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Empirical Potential ◽  
Silicon Nanotubes ◽  
Cohesive Energies

AbstractUsing two different approaches: Monte Carlo simulations with Tersoff empirical potential and first principles calculations, the energetics and the structural properties of double-walled carbon and silicon nanotubes are investigated. Through Tersoff potential, the changes on cohesive energies for the Si and C systems are determined for several outer tubules for a fixed inner tube. Adopting first principles calculations, based on density functional theory, the trends, in terms of the cohesive energies, are compared with the corresponding obtained results using Tersoff empirical potential. The structures, specially of the most stable double-walled nanotubes, are discussed.

scholarly journals First-Principles Determination of the Polarizabilities of Carbon Tubules as a Function of Length

1994 ◽  
Vol 349 ◽  
Author(s):  
Andrew A. Quong ◽  
Mark R. Pederson
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Valence Electron ◽  
Local Density ◽  
Density Approximation ◽  
Functional Theory ◽  
Size Dependent ◽  
The Density Functional Theory ◽  
Linear And Nonlinear

ABSTRACTWe use the local-density-approximation to the density-functional theory to determine the axial polarizabilities of fullerene tubules as a function of length and winding topologies. Specifically, we present linear polarizabilities for tubules of composition C12H24, C36H24, C40H20 and C60H24. The size-dependent variation in the dipole-coupled gaps between pairs of occupied and unoccupied levels leads to enhancements in the polarizability per valence electron as the length of the tubule increases. The results are compared to recent densityfunctional based calculations of the linear and nonlinear polarizabilities for fullerene and benzene molecules.

Size-Dependent Adsorption of Styrene on Pd Clusters: A Density Functional Theory Study

2019 ◽  
Vol 123 (4) ◽  
pp. 2182-2188 ◽  
Author(s):  
Zhaoming Xia ◽  
Sai Zhang ◽  
Fuzhu Liu ◽  
Yuanyuan Ma ◽  
Yongquan Qu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Size Dependent ◽  
Pd Clusters
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