Comparison between Optimized Geometries and Vibrational Frequencies Calculated by the DFT Methods

1996 ◽  
Vol 100 (37) ◽  
pp. 15056-15063 ◽  
Author(s):  
A. A. El-Azhary ◽  
H. U. Suter
Keyword(s):  
Vibrational Frequencies ◽  
Dft Methods ◽  
Optimized Geometries

scholarly journals Vibrational Frequencies of Cerium-Oxide-Bound CO: A Challenge for Conventional DFT Methods

2020 ◽  
Vol 125 (25) ◽  
Author(s):  
Pablo G. Lustemberg ◽  
Philipp N. Plessow ◽  
Yuemin Wang ◽  
Chengwu Yang ◽  
Alexei Nefedov ◽  
...  
Keyword(s):  
Cerium Oxide ◽  
Vibrational Frequencies ◽  
Dft Methods

Theoretical investigation of five-coordinated manganese(III) oxophlorin with different axial ligands at various spin states using different DFT methods

2022 ◽  
pp. A-S
Author(s):  
Pezhman Mirmarghabi ◽  
Homayoon Bahrami
Keyword(s):  
Nbo Analysis ◽  
Axial Ligand ◽  
Spin States ◽  
Dft Methods ◽  
Quintet State ◽  
Axial Ligands ◽  
Pyramid Structure ◽  
Stability Of Complexes ◽  
D Orbitals ◽  
Optimized Geometries

The Mn(III)-oxophlorin complexes with imidazole, pyridine and t-butylcyanide as axial ligands have been studied using B3LYP, Bv86p, and M06-2X methods. All of the possible optimized geometries are specified, while the M06-2X is employed. Results obtained show that the isomers of Mn(III)-oxophlorin with imidazole or pyridine are the most stable at quintet state, compared to singlet and triplet spin states. Besides, there are two and four [Formula: see text]-electrons on manganese in each of these complexes at triplet and quintet states, respectively. Also, Mn(III)-oxophlorin with t-butylcyanide as axial ligand is only stable at singlet state. Non-specific solvent effects show that dispersion and London forces have the basic role in stability of complexes in a solvent. Note that latter interactions can occur in medium with dielectric constant ([Formula: see text]) of [Formula: see text]8, such as [Formula: see text] for position of oxophlorin in heme oxygenase enzyme. NBO analysis show that there is no degeneracy between d orbitals of Mn in the five-coordinated Mn(III)-oxophlorin at singlet and triplet spin states, but two d orbitals of manganese are degenerated in latter complexes at quintet state. Such degeneracy of d orbitals is observed in a complex with square pyramid structure. Then five-coordinated Mn(III)-oxophlorin with imidazole or pyridine is the most stable at quintet spin state, because of its geometry corresponding to square pyramid configuration of atoms. Also, nonbounding interaction between Mn and the ring of oxophlorin or Mn and ligand are more effective in Mn(III)-oxophlorin with imidazole as axial ligand, compared to pyridine and t-butylcyanide.

Computational investigation of isomeric and conformeric structures of methyl iodoperoxide

2005 ◽  
Vol 83 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Evangelos Drougas ◽  
Agnie M Kosmas
Keyword(s):  
Electronic Structure ◽  
Single Point ◽  
Transition States ◽  
Vibrational Frequencies ◽  
Basis Sets ◽  
Quantum Mechanical ◽  
Energy Structure ◽  
Computational Investigation ◽  
Electronic Structure Methods ◽  
Optimized Geometries

Quantum mechanical electronic structure methods are employed to investigate the isomeric and conformeric stuctures of methyl iodoperoxide. Optimized geometries and harmonic vibrational frequencies are calculated at the MP2 level of theory using two types of basis sets, the 6-311G(d,p) for all atoms and the 6-311G(d,p) combined with the LANL2DZ relativistic ECP procedure for iodine. Refinement of the energetics has been accomplished by performing single-point CCSD(T) calculations. Five isomers were determined in total among which iodomethyl hydroperoxide (ICH2OOH) is found to be the lowest energy structure. Conformational barriers and transition states that connect the isomeric forms have been characterized.Key words: methyl iodoperoxide, isomers, conformers.

Theoretical study on the effect of different π-linker on the performance of sensitizer in carbazole-based dyes

2018 ◽  
Vol 17 (02) ◽  
pp. 1850019 ◽  
Author(s):  
Huixia Guo ◽  
Xiaohua Xi ◽  
Renxiang Yan ◽  
Xiaoquan Lu
Keyword(s):  
Density Functional ◽  
Short Circuit ◽  
Dye Sensitized Solar Cells ◽  
Photocurrent Density ◽  
Dft Methods ◽  
Functional Theory ◽  
Dye Sensitized ◽  
Sensitized Solar Cells ◽  
Maximum Absorption Wavelength ◽  
Optimized Geometries

Derived from diarylamine sensitizer diphenyl-(7-pyridin-4-yl-9H-carbazol-2-yl)-amine (N13), a series of novel D[Formula: see text]A carbazole-based organic dye sensitizers with different [Formula: see text]-linkers were designed for searching more effective sensitizers in dye-sensitized solar cells (DSSCs) design. Optimized geometries, electronic structure, and other parameters, which can evaluate the performance of DSSCs effectively and intuitively, were theoretically calculated by density functional theory (DFT) and time-dependent DFT methods at the M06/6-31G(d,p) level. The results indicated that the maximum absorption wavelength of designed dye was red-shifted and the molar absorption coefficient ([Formula: see text]) became higher. This phenomenon can be explained by the modification of the [Formula: see text]-bridge. The simulated Ultraviolet–visible spectroscopy (UV-Vis) absorption spectrum showed that the designed N,N-diphenyl-7-(5-(7-(5-(pyridin-4-yl)thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-9H-carbazol-2-amine (N22) dye presents the largest red-shifted absorption band and the designed (E)-N,N-diphenyl-7-(2-(5[Formula: see text]-(pyridin-4-yl)-[2,2[Formula: see text]-bithiophene]-5-yl)vinyl)-9H-carbazol-2-amine (N21) dye showed the largest [Formula: see text], both of them depicted a high short-circuit photocurrent density ([Formula: see text]. Meanwhile, the charge separation hampered by long [Formula: see text]-linkers was also observed. These results are helpful for designing new sensitizers and providing effective guiding to experimental synthesis.

scholarly journals Erratum: Vibrational Frequencies of Cerium-Oxide-Bound CO: A Challenge for Conventional DFT Methods [Phys. Rev. Lett. 125 , 256101 (2020)]

2022 ◽  
Vol 128 (1) ◽  
Author(s):  
Pablo G. Lustemberg ◽  
Philipp Plessow ◽  
Yuemin Wang ◽  
Chengwu Yang ◽  
Alexei Nefedov ◽  
...  
Keyword(s):  
Cerium Oxide ◽  
Vibrational Frequencies ◽  
Dft Methods

An ab initio and AIM study on the decomposition of phosphite ozonides

2003 ◽  
Vol 81 (6) ◽  
pp. 525-534 ◽  
Author(s):  
Jeff L Langeland ◽  
Nick H Werstiuk
Keyword(s):  
Singlet Oxygen ◽  
Single Point ◽  
Activation Energies ◽  
Wave Functions ◽  
Atomic Charges ◽  
Trimethyl Phosphite ◽  
Triphenyl Phosphite ◽  
Dft Methods ◽  
Phosphite Ozonides ◽  
Optimized Geometries

DFT calculations at the Becke3PW91/6–31+G(d) level of theory provided optimized geometries, transition states, and wave functions suitable for the study of the reactivity and molecular structure with Atoms-in-molecules (AIM) of phosphite ozonide complexes. These calculations also provided activation energies for the extrusion of singlet oxygen from the ozonides, which occurs in a concerted manner. The molecular species investigated were trimethyl phosphite ozonide (1), triphenyl phosphite ozonide (2), trifluoromethyl phosphite ozonide (3), trifluoroethyl phosphite ozonide (4), 4-ethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane ozonide (5), 1-phospha-2,6,7-trioxabicyclo[2.2.2]octane ozonide (6), 1-phospha-2,8,9-trioxadamantane ozonide (7), and propylene phenyl phosphite ozonide (8). Single-point calculations at the Becke3PW91/6–311++G(d,p) level on the geometries obtained from the lower level theory yielded activation energies of 15.1 and 16.4 kcal mol–1 for the nonconstrained complexes 1 and 2, respectively. These values differed from the electronegative trifluoro derivatives 3 and 4, which had much higher barriers of 23.5 and 20.8 kcal mol–1, respectively. The activation energies of the bicyclic complexes 5–7 were significantly higher than 1 and 2 and comparable to 3 and 4, ranging from 23 to 26 kcal mol–1. An intermediate barrier of 20.5 kcal mol–1 was computed for 8. AIMPAC studies showed no direct correlation between the AIM atomic charges on the phosphorus or oxygen atoms of the ozonide ring with the ease of decomposition of 1–8 to singlet oxygen and the corresponding phosphate.Key words: phosphite ozonide complexes, decomposition, DFT methods, AIM, activation energy.

scholarly journals Quantum Mechanical Modeling of the Vibrational Spectra of Minerals with a Focus on Clays

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 141 ◽  
Author(s):  
James Kubicki ◽  
Heath Watts
Keyword(s):  
Vibrational Spectra ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Isotopic Fractionation ◽  
Inelastic Neutron ◽  
Vibrational Frequencies ◽  
Quantum Mechanical ◽  
Dft Methods ◽  
Additional Information ◽  
Starting Point

We present an overview of how to use quantum mechanical calculations to predict vibrational frequencies of molecules and materials such as clays and silicates. Other methods of estimating vibrational frequencies are mentioned, such as classical molecular dynamics simulations; references are given for additional information on these approaches. Herein, we discuss basic vibrational theory, calculating Raman and infrared intensities, steps for creating realistic models, and applications to spectroscopy, thermodynamics, and isotopic fractionation. There are a wide variety of programs and methods that can be employed to model vibrational spectra, but this work focuses on hybrid density functional theory (DFT) approaches. Many of the principles are the same when used in other programs and DFT methods, so a novice can benefit from simple examples that illustrate key points to consider when modeling vibrational spectra. Other methods and programs are listed to give the beginner a starting point for exploring and choosing which approach will be best for a given problem. The modeler should also be aware of the numerous analytical methods available for obtaining information on vibrations of atoms in molecules and materials. In addition to traditional infrared and Raman spectroscopy, sum-frequency generation (SFG) and inelastic neutron scattering (INS) are also excellent techniques for obtaining vibrational frequency information in certain circumstances.

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