A density functional theory approach to the magnetic properties of a coupled single-molecule magnet (Mn7)2 complex — An entangled qubit pair candidate

2013 ◽  
Vol 91 (9) ◽  
pp. 866-871 ◽  
Author(s):  
Silvia Gómez-Coca ◽  
Eliseo Ruiz
Keyword(s):  
Density Functional Theory ◽  
Single Molecule ◽  
Exchange Coupling ◽  
Density Functional ◽  
Relative Strength ◽  
Coupling Constants ◽  
Basis Set ◽  
Theory Approach ◽  
Functional Theory ◽  
Spin Configuration

The exchange coupling constants of a Mn14 complex constituted by two weakly coupled Mn7 moieties were calculated using two different density functional theory (DFT) approaches: the Perdew–Burke–Ernzerhof (PBE) functional with a numerical basis set and the hybrid Becke, three-parameter Lee–Yang–Parr (B3LYP) functional employed with a Gaussian basis set. The sign and relative strength of the exchange coupling constants calculated with both methods were consistent; as expected, the values calculated with the PBE functional were slightly overestimated, as corroborated by comparison with the experimental magnetic susceptibility curve. Both methods gave a ground spin configuration of S = 3/2 for the Mn7 moiety, which was weakly antiferromagnetically coupled with the other Mn7 fragment, leading to an S = 0 ground spin configuration for the entire Mn14 complex.

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Coupling Constants ◽  
Spin Projection ◽  
Coupling Constant ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

Spectroscopic and Bioactivity Analysis of Naturally Occurring Methyl Ester of Chlorogenic Acid Using Density Functional Theory Based Quantum Chemical Computation

2019 ◽  
Vol 17 (10) ◽  
pp. 822-825 ◽  
Author(s):  
Ashok Kumar Mishra ◽  
Satya Prakash Tewari
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Density Functional ◽  
Basis Set ◽  
Theory Approach ◽  
Functional Theory ◽  
Naturally Occurring ◽  
Quantum Chemistry Calculations ◽  
Spectroscopic Characteristics ◽  
Title Molecule

The present study describes the spectroscopic characteristics like IR and Raman active vibrations, (1H, 13C) nuclear magnetic resonance (NMR) chemical shifts and UV-Visible spectra of the molecular geometry obtained using quantum chemistry calculations based on density functional theory approach via B3LYP hybrid functional at 6-31 + G(d, p) basis set of title bioactive natural compound. The calculated highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap in titled compound is –0.14327 eV which is reasonably small and may be the prime reason for its bioactivity. Theoretical IR active vibration spectra show the maximum peak at 1146 cm–1. The maximum absorption in UV-Vis spectrum has been observed to be occurred at 329 nm. The biological activity has also been examined through virtual screening using molecular docking approach. The calculated spectroscopic characteristics are well aligned with their experi- mental counterparts. The obtained docking score predicts the title molecule to be a good naturally occurring anti diabetic agent. The outcomes of our investigation would be useful for deriving the structural analog of the title molecule for developing an efficient naturopathic anti diabetic drug agent with less side effects.

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Functional Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Geometry Optimization ◽  
Coupling Constants ◽  
Spin Projection ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of $J$-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Projection model provides an affordable and practical approach for effectively correcting spin-contamination errors in such calculations.

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Functional Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Geometry Optimization ◽  
Coupling Constants ◽  
Spin Projection ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of $J$-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Projection model provides an affordable and practical approach for effectively correcting spin-contamination errors in such calculations.

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