Theoretical Studies on the Structure and Spectroscopic Properties of 2,4-D (2,4-Diclorofenoxiacetic Acid)

2012 ◽  
Vol 2 (1) ◽  
pp. 1-11
Author(s):  
María G. Andino ◽  
Mariela I. Profeta ◽  
Jorge M. Romero ◽  
Nelly L. Jorge ◽  
Eduardo A. Castro
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Spectroscopic Properties ◽  
Uv Spectra ◽  
Basis Set ◽  
Basis Sets ◽  
Electronic Effects ◽  
B3lyp Method ◽  
Molecular Stability ◽  
2,4 Dichlorophenoxyacetic Acid

The 2,4-dichlorophenoxyacetic acid (2,4-D) is applied to and recovered from the leaf surfaces of garden bean and corn plants. This paper examines the theoretical study of the 2,4-D IR and UV spectra as well as the determination of its optimized molecular structure. Theoretical calculations are performed at the density functional theory (DFT) levels. The different structural and electronic effects determining the molecular stability of the conformers are discussed in a comparative fashion. The optimized geometry was calculated via the B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets and the FT-IR spectra was calculated by the density functional B3LYP method with the 6-311++G(d,p) basis set. The scaled theoretical wavenumbers show good agreement with the experimental values. A detailed interpretation of the infrared spectra of 2,4-D is reported.

Theoretical Studies on the Structure and Spectroscopic Properties of 2,4-D (2,4-Diclorofenoxiacetic Acid)

2013 ◽  
pp. 180-190
Author(s):  
María G. Andino ◽  
Mariela I. Profeta ◽  
Jorge M. Romero ◽  
Nelly L. Jorge ◽  
Eduardo A. Castro
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Basis Sets ◽  
Dichlorophenoxyacetic Acid ◽  
Electronic Effects ◽  
B3lyp Method ◽  
Detailed Interpretation ◽  
Corn Plants ◽  
Experimental Values ◽  
2,4 Dichlorophenoxyacetic Acid

The 2,4-dichlorophenoxyacetic acid (2,4-D) is applied to and recovered from the leaf surfaces of garden bean and corn plants. This paper examines the theoretical study of the 2,4-D IR and UV spectra as well as the determination of its optimized molecular structure. Theoretical calculations are performed at the density functional theory (DFT) levels. The different structural and electronic effects determining the molecular stability of the conformers are discussed in a comparative fashion. The optimized geometry was calculated via the B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets and the FT-IR spectra was calculated by the density functional B3LYP method with the 6-311++G(d,p) basis set. The scaled theoretical wavenumbers show good agreement with the experimental values. A detailed interpretation of the infrared spectra of 2,4-D is reported.

AlN Nanotubes: A DFT Study of Al-27 and N-14 Electric Field Gradient Tensors

2007 ◽  
Vol 62 (12) ◽  
pp. 711-715 ◽  
Author(s):  
Ahmad Seif ◽  
Mahmoud Mirzaei ◽  
Mehran Aghaie ◽  
Asadollah Boshra
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Density Functional ◽  
Quadrupole Coupling Constant ◽  
Basis Set ◽  
Basis Sets ◽  
B3lyp Method ◽  
Package Program ◽  
Nqr Parameters

Density functional theory (DFT) calculations were performed to calculate the electric field gradient (EFG) tensors at the sites of aliminium (27Al) and nitrogen (14N) nuclei in an 1 nm of length (6,0) single-walled aliminium nitride nanotube (AlNNT) in three forms of the tubes, i. e. hydrogencapped, aliminium-terminated and nitrogen-terminated as representatives of zigzag AlNNTs. At first, each form was optimized at the level of the Becke3,Lee-Yang-Parr (B3LYP) method, 6-311G∗∗ basis set. After, the EFG tensors were calculated at the level of the B3LYP method, 6-311++G∗∗ and individual gauge for localized orbitals (IGLO-II and IGLO-III) types of basis sets in each of the three optimized forms and were converted to experimentally measurable nuclear quadrupole resonance (NQR) parameters, i. e. quadrupole coupling constant (qcc) and asymmetry parameter (ηQ). The evaluated NQR parameters revealed that the considered model of AlNNT can be divided into four equivalent layers with similar electrostatic properties.With the exception of Al-1, all of the three other Al layers have almost the same properties, however, N layers show significant differences in the magnitudes of the NQR parameters in the length of the nanotube. Furthermore, the evaluated NQR parameters of Al-1 in the Al-terminated form and N-1 in the N-terminated form revealed the different roles of Al (base agent) and of N (acid agent) in AlNNT. All the calculations were carried out using the GAUSSIAN 98 package program.

scholarly journals Comparative experimental and theoretical study on the molecular structure and spectroscopic properties of sideroxol isolated from Sideritis stricta and its electronic properties

2021 ◽  
Vol 9 (2) ◽  
pp. 94-107
Author(s):  
Akin Azizoglu ◽  
◽  
Zuleyha Ozer ◽  
Carikci Sema ◽  
Turgut Kilic ◽  
...  
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Spectroscopic Properties ◽  
Basis Set ◽  
Basis Sets ◽  
Polarization Functions ◽  
Nmr Properties ◽  
Theory And Experiments

Sideroxol, a kaurene diterpene, was obtained from the acetone extract of Sideritis stricta plant. The ground-state molecular geometry, vibrational frequencies, and NMR chemical shifts were also investigated by using various density functional theories and Pople basis sets. The computed geometries are in good conformity with the experimental data. The comparison between theory and experiments indicates that B3LYP and M06 methods with the 6-31G(d) basis set are able to provide satisfactory results for predicting vibrational and NMR properties. There seems to be no significant effect of addition of diffuse and polarization functions in the basis set used herein.

Benchmarking Density Functionals, Basis Sets, and Solvent Models in Predicting Thermodynamic Hydricities of Organic Hydrides

2021 ◽  
Author(s):  
Christina Yeo ◽  
Minh Nguyen ◽  
Lee-Ping Wang
Keyword(s):  
Density Functional ◽  
Mean Squared Error ◽  
Theoretical Calculations ◽  
Computational Cost ◽  
Hydrogen Gas ◽  
Basis Set ◽  
Basis Sets ◽  
Density Functionals ◽  
Solvent Models ◽  
Solvent Model

Many renewable energy technologies, such as hydrogen gas synthesis and carbon dioxide reduction, rely on chemical reactions involving hydride anions. When selecting molecules to be used in such applications, an important quantity to consider is the thermodynamic hydricity, which is the free energy required for a species to donate a hydride anion. Theoretical calculations of thermodynamic hydricity depend on several parameters, mainly the density functional, basis set, and solvent model. In order to assess the effects of the above three parameters, we carry out hydricity calculations for a set of molecules with known experimental hydricity values, generate linear �fits, and compare the R-squared, root-mean-squared error, and Akaike Information Criterion across different combinations of density functionals, basis sets, and solvent models. Based on these results we are able to quantify the accuracy of theoretical predictions of hydricity and recommend the parameters with the best compromise between accuracy and computational cost.

F2 storage by confinement inside carbon nanotubes

2016 ◽  
Vol 94 (1) ◽  
pp. 15-19 ◽  
Author(s):  
Wiem Felah Gtari ◽  
Bahoueddine Tangour
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Density Functional Theory Method ◽  
Van Der Waals Interactions ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Walled Carbon Nanotubes

Theoretical calculations have been achieved to study the interaction between the confined F2 molecule along the nanotube axis and perpendicular to it and armchair (n,n) single-walled carbon nanotubes with n = 4, 5, 6, 7, and 8 and the zig-ag nanotube (9,0) using the density functional theory method with the CAM-B3LYP functional and both cc-pVQZ and STO-3G basis sets. The interaction of the F2 molecule with the nanotube is different according to the molecular orientation, the chirality of the carbon nanotube, and the confinement space extension. These results interpreted by means of van der Waals interactions reveal anisotropic and competitive behavior at the nanometric level. The π electrons of the nanotube interact with the lone pairs of F2 highlighting its lateral polarizability. The encapsulated F2 molecule is stable along and perpendicular to the nanotube (5,5) and (6,6) axis. The best stabilization energy is obtained fornanotube (5,5) at the perpendicular position using the cc-pVQZ basis set.

THEORETICAL CHARACTERIZATION OF A HIGHLY ELECTROPHILIC CARBENE

2005 ◽  
Vol 04 (03) ◽  
pp. 823-832 ◽  
Author(s):  
JUAN F. VAN DER MAELEN URÍA ◽  
JAVIER RUIZ ◽  
SANTIAGO GARCÍA-GRANDA
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Basis Set ◽  
Basis Sets ◽  
Singlet Ground State ◽  
X Ray Diffraction ◽  
Dft Methods ◽  
Hartree Fock ◽  
Experimental Complex ◽  
Experimental Geometry

The experimental geometry obtained from single-crystal X-ray diffraction data for a metalladiphosphanyl carbene precursor is compared with the results of theoretical calculations made at the ab initio level by using Hartree–Fock (HF) and Density Functional Theory (DFT) methods over the carbene itself. Theoretical geometry optimizations for the singlet ground state of [ Mn(CO)4(PH2)2C: ]+ have been performed with several hybrid functionals and basis sets. Calculated geometries showed a perfect C 2v symmetry in the highest levels of calculation and were somewhat relaxed when compared with the experimental ones; for instance, with the largest basis set, the P–C–P angle found was 124.8°, whereas C–P bond distances were both 1.667 Å, compared to 103.5(3)° and 1.718(5) Å, respectively, from the experimental data. The absence of a ligand attached to the C : atom in the calculated structure, which is present in the form of iodine in the experimental complex, is probably responsible, to a certain extent, for the discrepancies. In addition to the structural computations, in order to theoretically quantify the highly electrophilic character expected for the carbene, electron affinities were calculated and found to be between 6.24 eV and 6.97 eV at different DFT levels of calculation, which confirmed the expectations. In this respect, a comparison with the analogous [Ru(CNH)4(PH2)2C:]2+ carbene is also made, showing the possibility of experimentally trapping the manganese carbene.

Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

2019 ◽  
Author(s):  
Kamal Batra ◽  
Stefan Zahn ◽  
Thomas Heine
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Absolute Error ◽  
Time Dependent ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
Framework Materials ◽  
Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

Quantum Mechanical Investigation of Geometrical Structure and Dynamic Behavior of h-BNNT (9,9-5) and h-AlNNT (9,9-5)Single-Walled Nanotubes: NBO Analysis

2019 ◽  
Vol 16 (9) ◽  
pp. 705-717
Author(s):  
Mehrnoosh Khaleghian ◽  
Fatemeh Azarakhshi
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Structural Parameters ◽  
Energy Levels ◽  
Nbo Analysis ◽  
Electronic Energy ◽  
Boron Nitride Nanotubes ◽  
Basis Set ◽  
B3lyp Method ◽  
Mechanical Investigation

In the present research, B45H36N45 Born Nitride (9,9) nanotube (BNNT) and Al45H36N45 Aluminum nitride (9,9) nanotube (AlNNT) have been studied, both having the same length of 5 angstroms. The main reason for choosing boron nitride nanotubes is their interesting properties compared with carbon nanotubes. For example, resistance to oxidation at high temperatures, chemical and thermal stability higher rather than carbon nanotubes and conductivity in these nanotubes, unlike carbon nanotubes, does not depend on the type of nanotube chirality. The method used in this study is the density functional theory (DFT) at Becke3, Lee-Yang-Parr (B3LYP) method and 6-31G* basis set for all the calculations. At first, the samples were simulated and then the optimized structure was obtained using Gaussian 09 software. The structural parameters of each nanotube were determined in 5 layers. Frequency calculations in order to extract the thermodynamic parameters and natural bond orbital (NBO) calculations have been performed to evaluate the electron density and electrostatic environment of different layers, energy levels and related parameters, such as ionization energy and electronic energy, bond gap energy and the share of hybrid orbitals of different layers.

scholarly journals Photochemistry of 1-Phenyl-4-Allyl-Tetrazol-5-One: A Theoretical Study Contribution towards Mechanism Elucidation

2021 ◽  
Vol 11 (9) ◽  
pp. 4045
Author(s):  
Amilcar Duque-Prata ◽  
Carlos Serpa ◽  
Pedro J. S. B. Caridade
Keyword(s):  
Density Functional ◽  
Reaction Pathway ◽  
Intramolecular Proton Transfer ◽  
Polarizable Continuum Model ◽  
Uv Spectra ◽  
Point Of View ◽  
Basis Set ◽  
Pathway Evolution ◽  
Photodegradation Mechanism ◽  
Energetic Point

The photodegradation mechanism of 1-phenyl-4-allyl-tetrazol-5-one has been studied using (time-dependent) density functional theory with the M06-HF, B3LYP, and PBE0 functionals and the VDZ basis set. All calculations have been carried out using the polarizable continuum model to simulate the solvent effects of methanol. The reaction pathway evolution on the triplet state has been characterised to validate a previously postulated experimental-based mechanism. The transition states and minimums have been initially located by local scanning in partial constrained optimisation, followed by a fully relaxed search procedure. The UV spectra has shown to be better described with PBE0 functional when compared with the experimental results, having the M06-HF a shift of 40 nm. From the energetic point of view, the postulated mechanism has been validated in this work showing a concerted photoextrusion of the N2 molecule. The intramolecular proton transfer occurs at a later stage of the mechanism after cyclization of the allyl group on a triplet biradical intermediate. The photoproduct observed experimentally, a pyrimidinone, has been characterised. The infrared spectroscopic reaction profile has also been proposed.

REEXAMINATION OF LOW ENERGY STRUCTURES OF ${\rm Au}_{4}^{-}$ AND Au4

2010 ◽  
Vol 09 (supp01) ◽  
pp. 1-7 ◽  
Author(s):  
YI GAO ◽  
YU ZHAO ◽  
X. C. ZENG
Keyword(s):  
Free Energy ◽  
Density Functional ◽  
Photoelectron Spectrum ◽  
Global Minimum ◽  
Low Energy ◽  
Basis Sets ◽  
Cluster Method ◽  
Energy Calculation ◽  
Couple Cluster ◽  
B3lyp Method

Low energy isomers of [Formula: see text] and Au4 were reexamined using the hybrid density functional B3LYP method and the couple-cluster method with the aug-cc-pVDZ-PP and aug-cc-pVTZ-PP basis sets. For [Formula: see text], the B3LYP method favors the zigzag isomer and the second order Moller–Plesset perturbation (MP2) total energy calculation favors the D2h rhombus isomer, whereas the couple-cluster singles and doubles with perturbative triples [CCSD(T)] level of theory favors the Y-shaped C2v isomer. The pyramid isomer is much higher in energy and could be easily excluded. The Gibbs free energy correction based on harmonic approximation suggests that the zigzag isomer is lower in free energy than the D2h rhombus isomer at 298.15 K. These results confirm that the Y-shaped C2v isomer is the global minimum at both 0 K and room temperature and is thus the major isomer to account for the experimental photoelectron spectrum. The zigzag isomer is suggested, as a minor isomer, to account for the weak second peak at 3.40 eV in the experimental photoelectron spectrum. For neutral Au4 , the zigzag isomer is more stable than D2h rhombus isomer at the B3LYP level and the D2h rhombus isomer is the global minimum on basis of all post Hartree–Fock levels of theory.

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