A Comprehensive Computational Study on OCH+-Rg (Rg = He, Ne, Ar, Kr, Xe) Complexes

2003 ◽  
Vol 68 (3) ◽  
pp. 489-508 ◽  
Author(s):  
Yinghong Sheng ◽  
Jerzy Leszczynski
Keyword(s):  
Computational Study ◽  
Relativistic Effects ◽  
Dft Method ◽  
Basis Set ◽  
Rare Gas ◽  
Geometrical Parameters ◽  
Minor Effect ◽  
Dissociation Energies ◽  
Equilibrium Geometries

The equilibrium geometries, harmonic vibrational frenquencies, and the dissociation energies of the OCH+-Rg (Rg = He, Ne, Ar, Kr, and Xe) complexes were calculated at the DFT, MP2, MP4, CCSD, and CCSD(T) levels of theory. In the lighter OCH+-Rg (Rg = He, Ne, Ar) rare gas complexes, the DFT and MP4 methods tend to produce longer Rg-H+ distance than the CCSD(T) level value, and the CCSD-calculated Rg-H+ bond lengths are slightly shorter. DFT method is not reliable to study weak interaction in the OCH+-He and OCH+-Ne complexes. A qualitative result can be obtained for OCH+-Ar complex by using the DFT method; however, a higher-level method using a larger basis set is required for the quantitative predictions. For heavier atom (Kr, Xe)-containing complexes, only the CCSD method predicted longer Rg-H+ distance than that obtained at the CCSD(T) level. The DFT method can be applied to obtain the semiquantitative results. The relativistic effects are expected to have minor effect on the geometrical parameters, the H+-C stretching mode, and the dissociation energy. However, the dissociation energies are sensitive to the quality of the basis set. The nature of interaction between the OCH+ ion and Rg atoms was also analyzed in terms of the interaction energy components.

scholarly journals Ab initio study of the mechanism of the reaction ClO + O --> Cl + O2

2021 ◽  
Vol 66 (1) ◽  
Author(s):  
S. Naskar ◽  
G. Nandi ◽  
T. K. Ghosh
Keyword(s):  
Reaction Mechanism ◽  
Ab Initio ◽  
Minimum Energy ◽  
Transition States ◽  
Basis Set ◽  
Heat Of Reaction ◽  
Minimal Basis ◽  
Dissociation Energies ◽  
Correlation Consistent ◽  
Equilibrium Geometries

Abstract. Ab initio investigation on the reaction mechanism of ClO + O --> Cl + O2 reaction has been performed using correlation consistent triple zeta basis set. The geometry and frequency of the reactants, products, minimum energy geometries and transition states are obtained using MP2 method and energetics are obtained at the QCISD(T)//MP2 level of theory. Primarily, a possible reaction mechanism is obtained on the basis on IRC calculations using MP2 level of theory. To obtain true picture of the reaction path, we performed IRC calculations using CASSCF method with a minimal basis set 6-31G**. Some new equilibrium geometries and transition states have been identified at the CASSCF level. Energetics are also obtained at the QCISD(T)//CASSCF method. Possible reaction paths have been discussed, which are new in literature. Heat of reaction is found to be consistent with the experimental data. Bond dissociation energies to various dissociation paths are also reported.

scholarly journals Crystal structure, Hirshfeld surface analysis and computational study of 2-chloro-N-[4-(methylsulfanyl)phenyl]acetamide

2020 ◽  
Vol 76 (4) ◽  
pp. 594-598
Author(s):  
Sitthichok Mongkholkeaw ◽  
Apisit Songsasen ◽  
Tanwawan Duangthongyou ◽  
Kittipong Chainok ◽  
Songwut Suramitr ◽  
...  
Keyword(s):  
Surface Analysis ◽  
Title Compound ◽  
Crystal Packing ◽  
Computational Study ◽  
Dft Method ◽  
Hirshfeld Surface ◽  
Basis Set ◽  
Hirshfeld Surface Analysis ◽  
Compound C ◽  
Out Of Plane

In the title compound, C9H10ClNOS, the amide functional group –C(=O)NH– adopts a trans conformation with the four atoms nearly coplanar. This conformation promotes the formation of a C(4) hydrogen-bonded chain propagating along the [010] direction. The central part of the molecule, including the six-membered ring, the S and N atoms, is fairly planar (r.m.s. deviation of 0.014). The terminal methyl group and the C(=O)CH2 group are slightly deviating out-of-plane while the terminal Cl atom is almost in-plane. Hirshfeld surface analysis of the title compound suggests that the most significant contacts in the crystal are H...H, H...Cl/Cl...H, H...C/C...H, H...O/O...H and H...S/S...H. π–π interactions between inversion-related molecules also contribute to the crystal packing. DFT calculations have been performed to optimize the structure of the title compound using the CAM-B3LYP functional and the 6–311 G(d,p) basis set. The theoretical absorption spectrum of the title compound was calculated using the TD–DFT method. The analysis of frontier orbitals revealed that the π–π* electronic transition was the major contributor to the absorption peak in the electronic spectrum.

scholarly journals Ultrasound Assisted Synthesis, Molecular Structure,UV-Visible Assignments, MEP and Mulliken Charges Study of (E)-3-(4-chlorophenyl)-1-(4-methoxyphenyl) prop-2-en-1-one: Experimental and DFT Correlational

2021 ◽  
Vol 18 (1) ◽  
pp. 86-96
Author(s):  
Rohit S. Shinde
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Method ◽  
Atomic Charge ◽  
Dft Method ◽  
Basis Set ◽  
Geometrical Parameters ◽  
Functional Theory ◽  
Vibrational Assignments ◽  
Uv Visible

Present investigation deals with the synthesis and density functional theory study (DFT) of a chalcone derivative; (E)-3-(4-chlorophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (CPMPP). The synthesis of a CPMPP has been carried out by the reaction of 4-methoxyacetophenone and 4-chlorobenzalehyde in ethanol at 30 ℃ under ultrasound irradiation. The structure of a synthesized chalcone is affirmed on the basis of FT-IT, 1H NMR and 13C NMR. The geometry of a CPMPP is optimized by using the density functional theory method at the B3LYP/6-31G(d,p) basis set. The optimized geometrical parameters like bond length and bond angles have been computed. The absorption energies, oscillator strength, and electronic transitions have been derived at the TD-DFT method at the B3LYP/6-31G(d,p) level of theory for B3LYP/6-31G(d p) optimized geometries. The effect of polarity on the absorption energies is discussed by computing UV-visible results in dichloromethane (DCM). Since theoretically obtained wavenumbers are typically higher than experimental wavenumbers, computed wavenumbers were scaled with a scaling factor, and vibrational assignments were made by comparing experimental wavenumbers to scaled theoretical wavenumbers. Quantum chemical parameters have been determined and examined. Molecular electrostatic potential (MEP) surface plot analysis has been carried out at the same level of theory. Mulliken atomic charge study is also discussed in the present study.

New Chalcone Derivative: Synthesis, Characterization, Computational Studies and Antioxidant Activity

2019 ◽  
Vol 17 (1) ◽  
pp. 46-53
Author(s):  
Reşat Ustabaş ◽  
Nevin Süleymanoğlu ◽  
Namık Özdemir ◽  
Nuran Kahriman ◽  
Ersan Bektaş ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Density Functional ◽  
Computational Study ◽  
Dft Method ◽  
Basis Set ◽  
Basis Sets ◽  
Isomeric Form ◽  
Compound I ◽  
Chalcone Derivative ◽  
Reducing Ability

A new chalcone derivative, called as 1-(4-(benzylideneamino)phenyl)-3-(furan-2-yl)prop-2- en-1-one (I), was synthezised and characterized by spectral methods (infrared (IR) and proton and carbon- 13 nuclear magnetic resonance (1H- and 13C-NMR) spectroscopy). A computational study was performed by the density functional theory (DFT) method. Spectral data of compound I optimized by using 6-311G(d,p) and 6-311++G(d,p) basis sets were obtained by 6-311++G(d,p) basis set. The E-Z isomerism for newly synthesized chalcone derivative was investigated by considering four isomeric form, E/E, E/Z, Z/E and Z/Z. The results show that, as assumed and thus named, the chalcone derivative is in the E/E form. In addition, quantum chemical parameters were calculated by using DFT method with 6-311++G(d,p) basis set. Antioxidant activity of compound I was determined by the ferric reducing ability of plasma (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay methods. Compound I has low antioxidant activity.

Interactions of MKrn+ (M = Cu, Ag, and Au; n = 1 - 3): Ab Initio Calculations

2009 ◽  
Vol 62 (2) ◽  
pp. 121 ◽  
Author(s):  
Li Xinying ◽  
Cao Xue ◽  
Zhao Yongfang
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Theoretical Estimate ◽  
Relativistic Effects ◽  
Dissociation Energies ◽  
Population Analyses ◽  
Covalent Contribution ◽  
Equilibrium Geometries

The equilibrium geometries, stabilities, and populations of the title species were investigated at the CCSD(T) level. The population analyses show covalent contribution occurs in the M–Kr bonding and the best theoretical estimate of the dissociation energies of the most stable AuKrn+ are 0.801, 1.743, and 2.193 eV. The electron correlation and relativistic effects on the interaction were investigated at the CCSD(T) level and both effects stabilize the title species.

Basis set effects in simple compounds of heavy rare gases

2013 ◽  
Vol 91 (9) ◽  
pp. 894-901 ◽  
Author(s):  
Amelia Fitzsimmons ◽  
Mariusz Klobukowski
Keyword(s):  
Density Functional ◽  
Relativistic Effects ◽  
Basis Set ◽  
Basis Sets ◽  
Rare Gas ◽  
Rare Gases ◽  
Functional Theory ◽  
Model Core Potentials ◽  
Moller Plesset ◽  
Decomposition Pathway

Rare-gas hydrides of the type HRgX (Rg = Xe or Rn and X = F, Cl, Br, or I) have been studied using Møller–Plesset and density functional theory methods. Six model core potentials and their associated basis sets were used, with relativistic effects included implicitly. The effects of polarization, correlating, and diffuse basis functions were investigated. Molecular geometries of the metastable hydrides and transition states along the decomposition pathway were computed together with corresponding energies of formation and decomposition. The results of quantum theory of atoms in molecules analysis further elucidate the interactions between atoms in HRgX species and confirm the results of analyses obtained from the natural bond orbitals approach.

Theoretical study of spectroscopic constants and anharmonic force field of formaldehyde

2014 ◽  
Vol 13 (06) ◽  
pp. 1450049 ◽  
Author(s):  
Xuejun Wang ◽  
Meishan Wang ◽  
Chuanlu Yang ◽  
Jing Li ◽  
Dianmin Tong
Keyword(s):  
Force Field ◽  
Theoretical Data ◽  
Dft Method ◽  
Force Constants ◽  
Coupling Constants ◽  
Basis Set ◽  
Basis Sets ◽  
Spectroscopic Constants ◽  
Equilibrium Geometries ◽  
Anharmonic Force

The equilibrium geometries of formaldehyde are optimized with B3LYP, B3PW91 and MP2 methods employing three basis sets 6-311++G(2d,2p), aug-cc-pVTZ and cc-pVTZ, respectively, which agree well with the corresponding experimental and previous theoretical data. The best optimized geometries are obtained at the theoretical level B3LYP/6-311++G(2d,2p) basis set. Basing on the calculated equilibrium geometries, the spectroscopic constants and anharmonic force field of H 2 CO are investigated. The results show that DFT method is superior to MP2 method at the calculation of spectroscopic constants and force constants of H 2 CO . The vibration–rotation interaction constants and fundamental vibrational wave numbers of H 2 CO are firstly theoretically calculated. The Coriolis coupling constants, cubic force constants and most of quartic force constants are firstly theoretically predicted.

DFT Benchmark Study of the O--O Bond Dissociation Energy in Peroxides Validated with High-Level Ab-Initio Calculations

2019 ◽  
Author(s):  
Danilo Carmona ◽  
Pablo Jaque ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Reference Value ◽  
Basis Set ◽  
Basis Sets ◽  
Mean Deviation ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
The Mean ◽  
Experimental Values ◽  
High Level ◽  
Almost All

<div><div><div><p>Peroxides play a central role in many chemical and biological pro- cesses such as the Fenton reaction. The relevance of these compounds lies in the low stability of the O–O bond which upon dissociation results in radical species able to initiate various chemical or biological processes. In this work, a set of 64 DFT functional-basis set combinations has been validated in terms of their capability to describe bond dissociation energies (BDE) for the O–O bond in a database of 14 ROOH peroxides for which experimental values ofBDE are available. Moreover, the electronic contributions to the BDE were obtained for four of the peroxides and the anion H2O2− at the CBS limit at CCSD(T) level with Dunning’s basis sets up to triple–ζ quality provid- ing a reference value for the hydrogen peroxide anion as a model. Almost all the functionals considered here yielded mean absolute deviations around 5.0 kcal mol−1. The smallest values were observed for the ωB97 family and the Minnesota M11 functional with a marked basis set dependence. Despite the mean deviation, order relations among BDE experimental values of peroxides were also considered. The ωB97 family was able to reproduce the relations correctly whereas other functionals presented a marked dependence on the chemical nature of the R group. Interestingly, M11 functional did not show a very good agreement with the established order despite its good performance in the mean error. The obtained results support the use of similar validation strategies for proper prediction of BDE or other molecular properties by DF Tmethods in subsequent related studies.</p></div></div></div>

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