Computational Studies of Electronic Structures and Hyperfine Interactions of Muonium in Tetraphenylgermane

2012 ◽  
Vol 620 ◽  
pp. 418-423
Author(s):  
Pek Lan Toh ◽  
Shukri Sulaiman ◽  
Mohamed Ismail Mohamed-Ibrahim
Keyword(s):  
Density Functional ◽  
Hyperfine Interactions ◽  
Geometry Optimization ◽  
Optimization Procedure ◽  
Dft Method ◽  
Equilibrium Structure ◽  
Coupling Constants ◽  
Local Energy Minimum ◽  
Phenyl Rings ◽  
Principle Density Functional Theory

The equilibrium structure of muoniatedtetraphenylgermane (GePh4Mu) was studied using the first principle Density Functional Theory (DFT) method. Three muonium (Mu) trapping sites were considered, namelyortho,meta, andparapositions on one of the phenyl rings. Geometry optimization procedure was utilized to determine the local energy minimum for all the systems. The total energies corresponding to Mu at the three positions are very similar to each other. For themetacase, the corresponding energy is higher than the other two sites by only about 0.03 eV. The hyperfine parameters of Mu were also calculated. The Mu isotropic hyperfine coupling constants were found to be 441.85 MHz, 449.80 MHz, and 439.01 MHz for theortho,meta, andparacases, respectively. The anisotropic value was calculated to be very small.

Density Functional Theory Studies of Electronic Structures and Hyperfine Interactions of Muonium in Imidazole

2015 ◽  
Vol 749 ◽  
pp. 134-138 ◽  
Author(s):  
Pek Lan Toh ◽  
Shukri Sulaiman ◽  
Mohamed Ismail Mohamed Ibrahim ◽  
Lee Sin Ang
Keyword(s):  
Density Functional Theory ◽  
Electronic Structures ◽  
Density Functional ◽  
Hyperfine Interactions ◽  
Geometry Optimization ◽  
Optimization Procedure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Total Energies ◽  
Structure Calculations

We carried out ab initio electronic structure calculations in the frameworks of the Density Functional Theory (DFT) to study the electronic structures and hyperfine interaction of muonium (Mu) in imidazole (C3H4N2) and 1–methylimidazole (CH3C3H3N2). The local energy minima and hyperfine interactions of the Mu trapped at the three studies sites were determined by performing geometry optimization procedure. The results show the total energies for all three studied sites are close to one another. The Mu hyperfine interactions were also determined, with the corresponding values vary from 343.00 MHz to 471.28 MHz for the imidazole–Mu cluster, and from 380.21 MHz – 465.57 MHz to 475.93 MHz for the cluster of 1–methylimidazole–Mu, respectively.

scholarly journals Boron-Decorated Pillared Graphene as the Basic Element for Supercapacitors: An Ab Initio Study

2021 ◽  
Vol 11 (8) ◽  
pp. 3496
Author(s):  
Dmitry A. Kolosov ◽  
Olga E. Glukhova
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Heat Of Formation ◽  
Basic Element ◽  
Supercapacitor Electrode ◽  
Functional Theory ◽  
Icosahedral Clusters ◽  
New Material ◽  
Principle Density Functional Theory ◽  
Specific Quantum

In this work, using the first-principle density functional theory (DFT) method, we study the properties of a new material based on pillared graphene and the icosahedral clusters of boron B12 as a supercapacitor electrode material. The new composite material demonstrates a high specific quantum capacitance, specific charge density, and a negative value of heat of formation, which indicates its efficiency. It is shown that the density of electronic states increases during the addition of clusters, which predictably leads to an increase in the electrode conductivity. We predict that the use of a composite based on pillared graphene and boron will increase the efficiency of existing supercapacitors.

Enhancing the utility of 1JCH coupling constants in structural studies through optimized DFT analysis

2019 ◽  
Vol 55 (41) ◽  
pp. 5781-5784 ◽  
Author(s):  
Alexei V. Buevich ◽  
Josep Saurí ◽  
Teodor Parella ◽  
Nunziatina De Tommasi ◽  
Giuseppe Bifulco ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Geometry Optimization ◽  
Dft Method ◽  
High Accuracy ◽  
Coupling Constants ◽  
Structural Studies ◽  
Careful Selection ◽  
Selection Of

High accuracy for DFT-predicted 1JCH-couplings can be achieved without ad hoc corrections or empirical scaling by careful selection of the DFT method utilized for geometry optimization and J-coupling calculations.

scholarly journals Study of Substituent Effect on Properties of Platinum(II) Porphyrin Semiconductor Using Density Functional Theory

2018 ◽  
Vol 18 (4) ◽  
pp. 742
Author(s):  
Harno Dwi Pranowo ◽  
Fadjar Mulya ◽  
Hafiz Aji Aziz ◽  
Grisani Ambar Santoso
Keyword(s):  
Substituent Effect ◽  
Density Functional ◽  
Geometry Optimization ◽  
Dft Method ◽  
Band Gap Energy ◽  
Functional Theory ◽  
Substituent Group ◽  
Partial Charges ◽  
Visible Spectra ◽  
Uv Visible

Study of substituent effect on properties of platinum(II) porphyrin had been performed using DFT method. The aim of the study is to investigate the effect of substituent group on the electronic and optical properties of the platinum(II) porphyrin. Geometry optimization was conducted using DFT/B3LYP/LANL2DZ to obtain molecular structure, electronic structure and energy profile. Band gap energy (Eg), the density of states (DOS), and UV-visible spectra are the semiconductor parameters to study. Computational results show that platinum(II) porphyrin and substituted platinum(II) porphyrin have properties of semiconductor based on Eg value, DOS, and UV-visible spectra. The results show that Mulliken partial charges of electron withdrawing substituents are higher than the electron donating substituents (CH3, OH, and NH2). Eg values of the complexes with respect to the substituents follow this order: NH2 < OH < NO2 < COOH < I < CH3 < Br < F < H, for DOSHOMO values, the order is CH3 < NO2 < I < OH < F < NH2 < COOH < Br < H and the maximum wavelength (λmax) for UV-visible adsorption spectra follows this order: NH2 > OH > COOH > NO2 > I > Br > CH3 > F > H. Molecules with smaller Eg and DOSHOMO values and higher λmax are considered as the most appropriate semiconductor materials. Our results show that Pt(II)P-NH2 has the smallest Eg and the highest λmax among other substituted platinum(II) porphyrin molecules. Therefore, Pt(II)P-NH2 are the most suitable semiconductor material based on the aforementioned criteria.

Geometry Optimization, UV/Vis, NBO, HOMO and LUMO, Excited State and Antioxidant Evaluation of Pyrimidine Derivatives

2020 ◽  
Vol 17 ◽  
Author(s):  
Siyamak Shahab ◽  
Masoome Sheikhi ◽  
Evgeni Kvasyuk ◽  
Aliaksei G. Sysa ◽  
Radwan Alnajjar ◽  
...  
Keyword(s):  
Density Functional ◽  
Antioxidant Properties ◽  
Geometry Optimization ◽  
Dft Method ◽  
Oscillator Strengths ◽  
Equilibrium Geometry ◽  
Pyrimidine Derivatives ◽  
Excitation Energies ◽  
Solvent Water ◽  
Homo And Lumo

: In this research, the four pyrimidine derivatives have been studied by using density functional theory (DFT/B3LYP/6-31G*) in solvent water for the first time. After quantum-chemical calculations, the title compounds have been synthesized. The electronic spectra of the new derivatives in a solvent water were performed by time-dependent DFT (TD-DFT) method. The equilibrium geometry, the HOMO and LUMO orbitals, MEP, excitation energies, natural charges, oscillator strengths for the molecules have also been calculated. NBO analysis has been calculated in order to elucidate the intramolecular, rehybridization and delocalization of electron density. These molecules have high antioxidant potential due to the planarity and formation of intramolecular hydrogen bonds. Antioxidant properties of the title compounds have been investigated and discussed.

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.

Computational, Experimental Structural Characterization and Molecular Docking Studies of 5,7-Dihydroxy-4-methoxyflavone against Cytochrome P450 Enzymes

2020 ◽  
Vol 5 (3) ◽  
pp. 197-207
Author(s):  
A. Harikrishnan ◽  
R. Madivanane
Keyword(s):  
Cytochrome P450 ◽  
Molecular Docking ◽  
Title Compound ◽  
Density Functional ◽  
Geometry Optimization ◽  
Dft Method ◽  
Cytochrome P450 Enzymes ◽  
Molecular Docking Study ◽  
Experimental Values ◽  
Vibrational Wavenumbers

In this work, the geometry optimization and harmonic vibrational wavenumbers of kaempferide (5,7-dihydroxy-4-methoxyflavone) were computed by density functional theory (DFT) method. Theoretically computed vibrational wavenumbers were compared with experimental values and the interpretation of the vibrational spectra has been studied. Frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) analysis of the title compound have been carried out. The 1H & 13C NMR, UV visible and electronic properties of the compound were investigated theoretically and compared with the experimental values. Molecular docking study of the compound against cytochrome P450 family enzymes (CYPs 1A1, 1A2, 3A4, 2C8, 2C9 and 2D6) were also studied and the results revealed that the title compound interact with human CYP2C8 enzymes with minimum binding energy of -9.43 kcal/mol. The compound forms hydrogen bond with the residues of Thr302, Thr305, Leu361, Val362, Cys435, Gln356 and Ala297. Thus, these studies assist to understand the inhibitory mechanism of kaempferide with CYP450 enzymes and may facilitate significant clinical implications in the prevention and treatment of various therapeutic diseases.

scholarly journals Two-dimensional polyaniline (C3N) from carbonized organic single crystals in solid state

2016 ◽  
Vol 113 (27) ◽  
pp. 7414-7419 ◽  
Author(s):  
Javeed Mahmood ◽  
Eun Kwang Lee ◽  
Minbok Jung ◽  
Dongbin Shin ◽  
Hyun-Jung Choi ◽  
...  
Keyword(s):  
Solid State ◽  
Single Crystals ◽  
Density Functional ◽  
Density Functional Theory Calculation ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Phenyl Rings ◽  
Device Applications ◽  
Principle Density Functional Theory

The formation of 2D polyaniline (PANI) has attracted considerable interest due to its expected electronic and optoelectronic properties. Although PANI was discovered over 150 y ago, obtaining an atomically well-defined 2D PANI framework has been a longstanding challenge. Here, we describe the synthesis of 2D PANI via the direct pyrolysis of hexaaminobenzene trihydrochloride single crystals in solid state. The 2D PANI consists of three phenyl rings sharing six nitrogen atoms, and its structural unit has the empirical formula of C3N. The topological and electronic structures of the 2D PANI were revealed by scanning tunneling microscopy and scanning tunneling spectroscopy combined with a first-principle density functional theory calculation. The electronic properties of pristine 2D PANI films (undoped) showed ambipolar behaviors with a Dirac point of –37 V and an average conductivity of 0.72 S/cm. After doping with hydrochloric acid, the conductivity jumped to 1.41 × 103 S/cm, which is the highest value for doped PANI reported to date. Although the structure of 2D PANI is analogous to graphene, it contains uniformly distributed nitrogen atoms for multifunctionality; hence, we anticipate that 2D PANI has strong potential, from wet chemistry to device applications, beyond linear PANI and other 2D materials.

First-Principles Study of Soliton Hyperfine Interactions in Polyacetylene

1990 ◽  
Vol 209 ◽  
Author(s):  
C. T. White ◽  
F. W. Kutzler ◽  
J. W. Mintmire ◽  
M. R. Cook
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Broad Band ◽  
Coupling Constants ◽  
Electron Nuclear Double Resonance ◽  
Neutral Radical ◽  
Fermi Contact ◽  
Spin Densities

ABSTRACTAll-trans-polyacetylene is considered the prototypical broad band gap quasi onedimensional organic semiconductor. Intrinsicsoliton defects have long been known to be important to the understanding of the observed properties of this system at low doping levels. Magnetic resonance techniques provide powerful experimental probes into the nature and environment of these neutral-radical defects. In an earlier work we showed that firstprinciples spin-polarized local density functional (LDF) methods reliably predict proton Fermi-contact coupling constants for planar, neutral, organic π-radicals. We have also used these methods to calculate the Fermi-contact proton coupling constants associated with the soliton defect in polyacetylene.Herein we compare the results of these earlier soliton calculations to results from recent electron-nuclear double-resonance (ENDOR) experiments. Our predicted ratio of the negative to positive spin densities is in good agreement with these ENDORstudies. The negative spin densities arise from spin-polarization effects which are found to cause the soliton level at midgap to be split by several tenths of an eV.

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