scholarly journals Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

2021 ◽  
Vol 11 (9) ◽  
pp. 3806
Author(s):  
Matteo Cococcioni ◽  
Andrea Floris
Keyword(s):  
Magnetic Anisotropy ◽  
Single Molecule ◽  
Molecular Complex ◽  
Density Functional ◽  
Magnetic Energy ◽  
Energy Landscape ◽  
Generalized Gradient ◽  
Insulator Surface ◽  
The Stability ◽  
Magnetic States

The magnetic states and the magnetic anisotropy barrier of a transition metal molecular complex, dimolybdenum tetraacetate, are investigated via density functional theory (DFT). Calculations are performed in the gas phase and on a calcite (10.4) bulk insulating surface, using the Generalized-Gradient Approximation (GGA)-PBE and the Hubbard-corrected DFT + U and DFT + U + V functionals. The molecular complex (denoted MoMo) contains two central metallic molybdenum atoms, embedded in a square cage of acetate groups. Recently, MoMo was observed to form locally regular networks of immobile molecules on calcite (10.4), at room conditions. As this is the first example of a metal-coordinated molecule strongly anchored to an insulator surface at room temperature, we explore here its magnetic properties with the aim to understand whether the system could be assigned features of a single molecule magnet (SMM) and could represent the basis to realize stable magnetic networks on insulators. After an introductory review on SMMs, we show that, while the uncorrected GGA-PBE functional stabilizes MoMo in a nonmagnetic state, the DFT + U and DFT + U + V approaches stabilize an antiferromagnetic ground state and several meta-stable ferromagnetic and ferrimagnetic states. Importantly, the energy landscape of magnetic states remains almost unaltered on the insulating surface. Finally, via a noncollinear magnetic formalism and a newly introduced algorithm, we calculate the magnetic anisotropy barrier, whose value indicates the stability of the molecule’s magnetic moment.

A Density Functional Study of Structure and Stability of Ni8, Ni8 + and Ni8 − Cluster

2005 ◽  
Vol 1 (4) ◽  
pp. 172-182 ◽  
Author(s):  
Patrizia Calaminici ◽  
Marcela R. Beltrán
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Binding Energies ◽  
Functional Study ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
The Stability ◽  
Anionic Cluster

Density functional calculations of neutral, cationic and anionic nickel octamer are presented. The structure optimization and frequency analysis were performed on the local density approximation (LDA) level with the exchange correlation functional by Vosko,Wilk and Nusair (VWN). Improved calculations for the stability were based on the generalized gradient approximation (GGA) where the exchange correlation functional of Perdew and Wang (PW) was used. For neutral, cationic and anionic cluster several isomers and different spin multiplicities were investigated in order to find the lowest structures. Structural parameters, relative energies, binding energies, harmonic frequencies, adiabatic ionization potential and electron affinity will be presented. The calculated values are compared with available experimental data.

Ab-initio DFT simulation of electronic and magnetic properties of Tin+1and FeTin clusters

2021 ◽  
Author(s):  
Rachida Haichour ◽  
Sofiane MAHTOUT
Keyword(s):  
Magnetic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Three Dimensional ◽  
Binding Energies ◽  
Chemical Hardness ◽  
Generalized Gradient ◽  
Cage Structure ◽  
Electronic And Magnetic Properties ◽  
The Stability

Abstract We report a computational investigation of the electronic and magnetic properties of neutral Tin+1and FeTin (n=1-10) clusters using ab-initio calculations based on density functional theory (DFT) within the generalized gradient approximation (GGA). The best structures for Tin+1and FeTin clusters are planar for size n<5, while from n = 5, they showed a compact three dimensional cage structure. For the best structures of the FeTin clusters, the Fe atoms favors the peripheral position with highest coordination with the neighboring Ti atoms. The evolution as a function of the size of the average binding energies (Eb/atom) and HOMO–LUMO gaps of Tin+1 and FeTin (n=1-10) clusters are studied. The stability results show that the Tin+1 clusters have relatively higher stability than the FeTin cluster with the same size. In addition, the vertical ionization potentials and electron affinities, chemical hardness and atomic magnetic moment of Tin+1and FeTin (n=1-10) clusters are also investigated.

Stability and Physicochemical Principles for Icosahedral Ti12X (X = Li to Xe) Clusters: A DFT Study

2008 ◽  
Vol 8 (5) ◽  
pp. 2475-2478
Author(s):  
M. Salazar-Villanueva ◽  
P. H. Hernandez Tejeda ◽  
J. F. Rivas-Silva ◽  
J. A. Ascencio
Keyword(s):  
Density Functional ◽  
Chemical Affinity ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Stable Clusters ◽  
The Density Functional Theory ◽  
The Stability ◽  
Chemical Selectivity ◽  
Homo Lumo

Results about stability, electronic structure and characteristic electronic properties are reported for cluster structures based on icosahedra structure with a composition of Ti12X (X = Li to Xe) within the generalized gradient approximation of the density functional theory. It is demonstrated that several elements allow an improvement on the stability of Ti13 by a doping process where the central atoms is substituted. C, Si, P, Co, Ge, Ru and Te lead to the largest gain in energy, while the HOMO-LUMO maximum gap distinguishes to just C, Si, P and Te as the most probable to be found in experimental samples. The analysis included physicochemical study of the most stable clusters to predict chemical affinity and new properties. Results reported here are in agreement with partial studies of Ti12X but because of the considered elements, a new scope is open of possible application mainly in the fields as sensors, catalysis and medicine, where the chemical selectivity is an important parameter.

Structural and elastic properties of ZrN and HfN: ab initio study

2014 ◽  
Vol 92 (9) ◽  
pp. 1058-1061 ◽  
Author(s):  
Anurag Srivastava ◽  
Bhoopendra Dhar Diwan
Keyword(s):  
Elastic Properties ◽  
Density Functional ◽  
Zirconium Nitride ◽  
Energy Calculation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Hafnium Nitride ◽  
Zinc Blende ◽  
The Density Functional Theory ◽  
The Stability

The present paper discusses the density functional theory based stability analysis of zirconium nitride and hafnium nitride in its rocksalt (B1), CsCl (B2), and zinc blende (B3) type phases. The ground state total energy calculation approach of the system has been used through the generalized gradient approximation parameterized with revised Perdew–Burke–Ernzerhof as exchange correlation functional. The present theoretical analysis confirms the stability trend of phases from most stable to less stable as B1 → B2 → B3. The study also reports the analysis of elastic properties of these nitrides in its most stable B1-type phase.

Magic Clusters in SixMg3 (x=1-10) Series: Potential Building Motifs for Inorganic Nanomaterials

2013 ◽  
Vol 24 ◽  
pp. 77-84 ◽  
Author(s):  
Debesh Ranjan Roy
Keyword(s):  
Density Functional ◽  
Alkaline Earth ◽  
Shell Closure ◽  
Generalized Gradient ◽  
Functional Formalism ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Magic Clusters ◽  
Inorganic Nanomaterials ◽  
The Stability

A detail investigation on the stability and electronic properties for a series of bimetallic (semiconductor-alkaline earth) clusters, viz., SixMg3(x=1-10) is performed in search for the exceptional or unusual stable motifs. A standard generalized gradient approximation (GGA) exchange-correlation functional, as proposed by Perdew, Burke and Ernzerhof (PBE) is employed for this purpose under the density functional formalism. The magic stability of the concerned clusters is explained using the jellium and aromaticity models. It is evident from the present study that the magic stability of Si7Mg3cluster arises due to the jellium shell closure whereas the same for Si4Mg3originates from the σ dominated aromaticity over its π counterpart.

scholarly journals Effect of Doping Concentration on Structural Stability and Formation Energy of the Fluorine Doped Hexagonal Molybdenum Dioxide (MoO2). A First Principle Study.

2021 ◽  
pp. 55-59
Author(s):  
Yakubu Tanko ◽  
Alhassan Shuaibu ◽  
Aminu Abdulrahman ◽  
Oyedare Olusola ◽  
Mustapha Isa ◽  
...  
Keyword(s):  
Bond Length ◽  
Density Functional ◽  
Formation Energy ◽  
Doping Concentration ◽  
Generalized Gradient ◽  
Molybdenum Dioxide ◽  
Functional Theory ◽  
Free Atoms ◽  
The Stability ◽  
Quantum Espresso

The structural properties of undoped and Fluorine doped Hexagonal Molybdenum dioxide (MoO2) with different doping concentrations have been calculated using Density Functional Theory (DFT) within Generalized Gradient Approximation (GGA) as implemented in Quantum Espresso (QE). The calculated results were for the formation energy of 4.17%, 8.33%, 12.5%, of F doped MoO2 are 232.5eV, 463.0eV, and 698.5eV respectively, which show the variation of energy based on the increase in the doping concentration that led to having the breakage of bond in the structure of the compound. The undoped and 4.17% of F doped MoO2 have three free atoms, which maintain the stability of the structure, but when the doping concentration was increased, the bond breaks simultaneously which led to having four and five free atoms for 8.33%, and 12.5% of F doped MoO2 respectively. This makes 4.17% of F doped MoO2 with 17.09Ry more stable. Similarly, the bond length of undoped MoO2 was 2.2505pm, but when doped with 4.17% of F it changes to 2.3030pm which indicates a greater stability of the structure concentrations of the dopant above 4.17% reduced the bond length, which made the structure less stable.

scholarly journals Magnetic properties of free-standing finite linear Co chains

2018 ◽  
Vol 64 (5) ◽  
pp. 483 ◽  
Author(s):  
Julio Cesar Hernandez-Herrejon ◽  
Rodrigo Chavez-Alcazar
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Density Functional ◽  
Finite Size ◽  
Anisotropy Energy ◽  
Spin Moment ◽  
Generalized Gradient ◽  
Free Standing ◽  
Magnetic Anisotropy Energy ◽  
Atomic Chains

The ground state magnetic properties of Co_N linear atomic chains with 1 ≤ N ≤ 10 are studied within density functional theory using the generalized gradient approximation . A linear scaling between the binding energy per atom and the inverse of the number of atoms in the chain is found. For the optimized geometries, our results show a dimerization effect for chains of few atoms but for bigger ones the phenomena disappear in the center but remains at the ends due to finite size effects. The spin moment, the orbital moment and the magnetic anisotropy energy were investigated. For large chains, the orbital and spin moments have a tendency to become uniform. Enhanced spin and orbital moments were found due to the reduced coordination number compared to the cobalt in bulk. The cobalt chain of five atoms has the biggest magnetic anisotropy energy with an outstanding 8 meV, suggesting that it could have applications in ultrahigh density magnetic memories and hard disk. 

scholarly journals Magnetic anisotropy and stability of Fe3Ga compounds

2021 ◽  
Vol 5 (4) ◽  
pp. 229-235
Author(s):  
T. M. Inerbaev ◽  
A. U. Abuova ◽  
A. K. Dauletbekova ◽  
F. U. Abuova ◽  
G. A. Kaptagay ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Density Functional ◽  
Anisotropy Energy ◽  
Magnetic Anisotropy Energy ◽  
Phonon Spectra ◽  
The Density Functional Theory ◽  
The Difference ◽  
Structure Lead ◽  
The Stability ◽  
Crystal Modifications

The magnetic anisotropy energy and the stability of crystal modifications of D03 and L21 of Fe3Ga compounds are studied with the density functional theory methods. The magnetic anisotropy energy of the D03 structure is more than twice the same value for the L21 structure. The features in the electronic structure lead to the difference in the magnitude of spin-orbit interaction, explaining the found effect. The L21 structure is more thermodynamically stable in the entire range of the considered pressures. Under pressure, the considered crystal modifications of Fe3Ga lose their stability due to the appearance of imaginary frequencies in their phonon spectra.

Novel Silicon–Carbon Fullerene-Like Nanostructures: An Ab Initio Study on the Stability of Si54C6 and Si60C6 Clusters

2006 ◽  
Vol 6 (1) ◽  
pp. 43-53
Author(s):  
Aravind Srinivasan ◽  
Asok K. Ray
Keyword(s):  
Density Functional ◽  
Basis Set ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Silicon Carbon ◽  
Double Zeta ◽  
Valence Electrons ◽  
Symmetry Constraints ◽  
Core Electrons ◽  
The Stability

Silicon fullerene like nanostructures with six carbon atoms on the surface of Si60 cages by substitution, as well as inside the cage at various symmetry orientations have been studied within the generalized gradient approximation to density functional theory. Full geometry optimizations have been performed without any symmetry constraints using the Gaussian 03 suite of programs and the LANL2DZ basis set. Thus, for the silicon atom, the Hay-Wadt pseudopotential with the associated basis set are used for the core electrons and the valence electrons, respectively. For the carbon atom, the Dunning/Huzinaga double zeta basis set is employed. Electronic and geometric properties of the nanostructures are presented and discussed in detail. It was found that optimized silicon–carbon fullerene like nanostructures have increased stability compared to bare Si60 cage and the stability depends on the orientation of carbon atoms, as well as on the nature of bonding between silicon and carbon atoms and also on the carbon–carbon bonding.

Tuning Structural and Electronic Properties of Phosphorene with Vacancies

2020 ◽  
Vol 6 (1) ◽  
pp. 7-15
Author(s):  
N. Pantha ◽  
B. Chauhan ◽  
P. Sharma ◽  
N. P. Adhikari
Keyword(s):  
Magnetic Properties ◽  
Band Gap ◽  
Density Functional ◽  
Formation Energy ◽  
Single Layer ◽  
Generalized Gradient ◽  
Geometrical Structures ◽  
Structural And Electronic Properties ◽  
The Stability ◽  
Quantum Espresso

Two dimensional materials show multiple applications including in semiconductor devices and gaseous storage. We have carried out First-Principles calculations to study the geometrical structures, stability and electronic/magnetic properties of pristine as well as double vacancy phospherene. Calculations are based on Density Functional Theory (DFT) taking an account of van der Waals (vdW) interaction in the DFT-D2 approach within Generalized Gradient Approximation (GGA). Modeling and simulation have been performed with Quantum ESPRESSO (QE) codes. The supercell of 4×4 structure, whose building block is an orthogonal unit cell with four phosphorous atoms, is used to model the samples. Based on the stability of defected single layer phosphorene, a couple of structures (DV(5|8|5)-1 and DV(5|8|5)-2) have been considered to calculate their formation energy, band structure and other properties. Formation energy values find the former structure (DV(5|8|5)-1) more favorable to create than the later one. A band gap of 0.86eV for pristine phospherene, an excellent agreement with the experiment, validates the results of present calculations. The phosphorene with double vacancy, however, shows significant changes in electronic bands with reference to the pristine one. The band gap for DV(5|8|5)-1 and DV(5|8|5)-2 systems are found to be 1.01eV and 0.1 eV respectively. No magnetic moment in both the pure and defected (double vacancy) phospherene monolayer approves that only the vacancies are not enough to induce magnetic properties in phosphorene.

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