Second row homopolar diatomic molecules. Potential curves, spectroscopic constants, and dissociation energies at the basis set limit for SCF and limited CI wave functions

1984 ◽  
Vol 80 (10) ◽  
pp. 5130-5140 ◽  
Author(s):  
A. D. McLean ◽  
B. Liu ◽  
G. S. Chandler
Keyword(s):  
Diatomic Molecules ◽  
Wave Functions ◽  
Basis Set ◽  
Spectroscopic Constants ◽  
Dissociation Energies ◽  
Potential Curves

Topological analysis of electron momentum densities and the bond directional principle: the first-row hydrides, AH, and homonuclear diatomic molecules, A2

1996 ◽  
Vol 74 (6) ◽  
pp. 1187-1191 ◽  
Author(s):  
Jiahu Wang ◽  
B. James Clark ◽  
Hartmut Schmider ◽  
Vedene H. Smith
Keyword(s):  
Diatomic Molecules ◽  
Topological Analysis ◽  
Momentum Density ◽  
Wave Functions ◽  
Basis Set ◽  
Electron Momentum ◽  
Hartree Fock ◽  
Topological Features ◽  
Homonuclear Diatomic Molecules ◽  
Slater Basis

Topological analysis of electron momentum densities of the first-row hydrides and homonuclear diatomic molecules has been carried out. The densities and their curvatures were calculated from wave functions of near Hartree–Fock quality using a Slater basis. The bond directional principle has been discussed through the topological properties of electron momentum densities. Basis set effects on the topological features have also been addressed. Key words: electron momentum density, the bond directional principle, topological analysis, first-row hydrides, homonuclear diatomic molecules.

Study of potential curves by UHF type methods. Inversion and dissociation of NH3 molecule

1984 ◽  
Vol 49 (8) ◽  
pp. 1731-1735 ◽  
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Saddle Point ◽  
Basis Set ◽  
Inversion Barrier ◽  
Exact Methods ◽  
Energy Parameters ◽  
Dissociation Energies ◽  
Bond Functions ◽  
Potential Curves ◽  
Good Agreement

Geometry and energy parameters of individual dissociation intermediate steps of the NH3 molecule, geometry of the saddle point, and the inversion barrier of NH3 have been calculated by the UMP2 method in the minimum basis set augmented with the bond functions. A good agreement has been reached with experimental data and with results of more exact methods except for the dissociation energies of the NH3 and NH2 molecules. New values of heats of formation are suggested on the basis of these results: ΔHfo0 = 197 and 362 kJ/mol for the NH2 and NH molecules, respectively.

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>

Study of potential curves by UHF type methods. CH4 molecule and its dissociation products

1986 ◽  
Vol 51 (4) ◽  
pp. 731-737
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Quantum Chemistry ◽  
High Energy ◽  
Basis Set ◽  
Electronic Correlation ◽  
Exact Methods ◽  
Energy Parameters ◽  
Bond Functions ◽  
The Individual ◽  
Potential Curves

Geometry and energy parameters of the individual dissociation intermediate steps of CH4 molecule, parameters of the barrier to linearity and singlet-triplet separation of the CH2 molecule have been calculated by means of the UMP method in the minimum basis set augmented with the bond functions. The results agree well with experimental data except for the geometry of CH2(1A1) and relatively high energy values of CH(2II) and CH2(1A1) where the existence of two UHF solutions indicates a necessity of description of the electronic correlation by more exact methods of quantum chemistry.

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 Potential Functions and Thermodynamic Properties of UC, UN, and UH

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Shuang-Ling Tang ◽  
Yu Wang ◽  
Qi-Ying Xia ◽  
Xue-Hai Ju
Keyword(s):  
Configuration Interaction ◽  
Density Functional ◽  
Least Square Method ◽  
Potential Functions ◽  
Least Square ◽  
Basis Set ◽  
Dissociation Energies ◽  
Anharmonicity Constant ◽  
Different Temperatures ◽  
Relationship Of

Potential energy surface scanning for UC, UN, and UH was performed by configuration interaction (CI), coupled cluster singles and doubles (CCSD) excitation, quadratic configuration interaction (QCISD (T)), and density functional theory PBE1 (DFT-PBE1) methods in coupling with the ECP80MWB_AVQZ + 2f basis set for uranium and 6 − 311 + G∗ for carbon, hydrogen, and nitrogen. The dissociation energies of UC, UN, and UH are 5.7960, 4.5077, and 2.6999 eV at the QCISD (T) levels, respectively. The calculated energy was fitted to the potential functions of Morse, Lennard-Jones, and Rydberg by using the least square method. The anharmonicity constant of UC is 0.0047160. The anharmonic frequency of UC is 780.27 cm−1 which was obtained based on the PBE1 results. For UN, the anharmonicity constant is 0.0049827. The anharmonic frequency is 812.65 cm−1 which was obtained through the PBE1 results. For UH, the anharmonicity constant is 0.017300. The anharmonic frequency obtained via the QCISD (T) results is 1449.8 cm−1. The heat capacity and entropy in different temperatures were calculated using anharmonic frequencies. These properties are in good accordance with the direct DFT-UPBE1 results (for UC and UN) and QCISD (T) results (for UH). The relationship of entropy with temperature was established.

Dissociation Energies of Diatomic Molecules

1960 ◽  
Vol 33 (5) ◽  
pp. 1541-1553 ◽  
Author(s):  
G. R. Somayajulu
Keyword(s):  
Diatomic Molecules ◽  
Dissociation Energies
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