The balance between theoretical method and basis set quality: A systematic study of equilibrium geometries, dipole moments, harmonic vibrational frequencies, and infrared intensities

1993 ◽  
Vol 99 (1) ◽  
pp. 403-416 ◽  
Author(s):  
J. Russell Thomas ◽  
Bradley J. DeLeeuw ◽  
George Vacek ◽  
T. Daniel Crawford ◽  
Yukio Yamaguchi ◽  
...  
Keyword(s):  
Systematic Study ◽  
Dipole Moments ◽  
Theoretical Method ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Infrared Intensities ◽  
Equilibrium Geometries

Conformational and Vibrational Analysis of 2-, 3- and 4-Pyridinecarbonyl Chloride Using DFT

2016 ◽  
Vol 230 (5-7) ◽  
Author(s):  
Sahar Abdalla ◽  
Yunusa Umar ◽  
Issraa Mokhtar
Keyword(s):  
Vibration Analysis ◽  
Density Functional ◽  
Dipole Moments ◽  
Vibrational Analysis ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Hybrid Density Functional ◽  
Optimized Geometries

AbstractThe conformation and vibration analysis of 2-, 3- and 4-pyridinecarbonyl chlorides have been computed using B3LYP hybrid density functional with 6-311++G** basis set. All structures have been fully optimized, and the optimized geometries, dipole moments, infrared vibrational frequencies and relative energies are reported. From the computations, 2-pyridinecarbonyl chloride is predicted to exist predominantly in

Density Functional Theory and ab initio Hartree-Fock Calculations of Molecular Structure and Vibrational Spectra of Anilinium Nitrate

2008 ◽  
Vol 63 (10-11) ◽  
pp. 712-720 ◽  
Author(s):  
Davut Avcı ◽  
Adil Başoğlu ◽  
Yusuf Atalay
Keyword(s):  
Molecular Structure ◽  
Density Functional Theory ◽  
Density Functional ◽  
Molecular Geometry ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Dft Methods ◽  
Functional Theory ◽  
Hartree Fock ◽  
Infrared Intensities

The molecular geometry, vibrational frequencies, infrared intensities, Raman scattering activities and several thermodynamic parameters of anilinium nitrate in the ground state have been calculated by both Hartree-Fock (HF) and three density functional theory (DFT) methods (B3LYP, BLYP and B3PW91) using the 6-31G(d) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray structure. The optimized geometric bond lengths are described very well by the HF method while bond angles are reproduced more accurately by the DFT methods. Comparison between the observed fundamental vibrational frequencies of anilinium nitrate and the results of DFT and HF methods indicates that B3LYP is superior to the scaled HF, BLYP and B3PW91 approaches for molecular vibrational problems. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. In addition, calculated results are related to the linear correlation plot of computed data versus experimental geometric parameters and IR data.

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.

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