Hartree-Fock calculation of the harmonic force constants and equilibrium geometry of formaldehyde

Meyer, Wilfried; Pulay, Péter

doi:10.1007/bf00527480

Cited by 92 publications

(7 citation statements)

References 34 publications

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“…The wagging force constant of formaldehyde deviates more from the experiment than the rock one in the case of the CNDO method. The same result has been obtained from ab initio calculations [10]. The MINDO method underestimates both couplings.…”

Section: Symmetry Force Constants Of Hchosupporting

confidence: 79%

Calculation of harmonic force constants by semiempirical methods

Kozmutza

1976

Acta Physica

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A systematic investigation on the harmonie force constants by the force method attached to CNDO/2 and MINDO/2 programs has been earried out.The force constants calculated for the HzO, NHs, CH, and HCHO ate in satisfactory agreement with experiment.The results obtained for CH3CHO may be useful for the experimental determination of the force fie]d too. IntroduetionThis work is a part of a systematie investigation on the harmonic foree eonstants of molecules by the force method [1]. The studies set out to obtain informations about the force field of largor systems the experimental data of whieh aro uncertain or the ab initio method is unable to calculate them. We have investigated whether from semiempirical Hartree--Fock type wavefunctions complete quadratie force fields can be determined [2]. In order to test our method the foree constants of H20, NH3, CHe, C2H6, C2H4, C2H2 and HCHO molecules have been determined. The harmonic force constants of CH3CHO have been calculated as well. The results of C2H6, C2H ` and C2H 2 have already been published [3].Two widely known semiempirical methods, the CNDO/2 [4,5] and the MINDO/2 [6,7] are used for the oalculations. CalculationsThe force method attached to the CNDO and MINDO programs [2,3] calculates the Cartesian forees at the end of the SCF iteration. Thesc foroes can be transformed to a set of internal, semi-symmetry or symmetry coordinatos. The foree constants are obtained as the numerical derivatives of forces with respect to the specified coordinates. The finito distortions from the reference geometry were -4-0.02 ~ (bond stretchings) and ~-2.0 ~ (deformations) in aH casos. Ca]cu]ations were carried out at the experimental geometry, the * Pext of a doctoral thesis at

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Section: Symmetry Force Constants Of Hchosupporting

confidence: 79%

Calculation of harmonic force constants by semiempirical methods

Kozmutza

1976

Acta Physica

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“…To obtain a good correlation with the experimental wavenumbers it is necessary to correct the calculated harmonic wavenumbers. For this purpose, one possible approach involves the rescaling of the force constant matrix, as proposed by Meyer and Pulay 19, 20. This procedure will certainly improve the agreement between computed and experimental wavenumbers.…”

Section: Introductionmentioning

confidence: 99%

Scaling factors for the prediction of vibrational spectra. II. The aniline molecule and several derivatives

Palafox

Gill

Núñez

et al. 2005

Int J of Quantum Chemistry

160

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ABSTRACT:The structure of aniline was studied by semiempirical, ab initio, and density functional methods. Complete geometry optimization of the minimum energy structure and of the transition states for internal rotation and inversion of the amino group was carried out using several levels. The performance of the different methods in calculating and describing the vibrational frequencies of aniline was determined. The normal modes were characterized by the magnitudes and direction of the displacement vectors. Three procedures were used to obtain the scaled frequencies, two of them new, using specific scale factors and scaling equations from the benzene molecule. The errors obtained were compared with those calculated through other standard procedures. A reassignment of several bands was made. A comparison of the cost-effective method and procedure of scaling was carried out.

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“…One possible approach involves the rescaling of the force constant matrix. A simple example is the proposal of Meyer and Pulay 2 to multiply all diagonal stretching force constants by 0.9 and to multiply all diagonal bending force constants by 0.8. This procedure will certainly improve the agreement between computed and experimental frequencies since the computed values are usually too high by 5–10%.…”

Section: Introductionmentioning

confidence: 99%

Scaling factors for the prediction of vibrational spectra. I. Benzene molecule

Palafox

2000

Int. J. Quant. Chem.

395

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The performance of semiempirical, ab initio, and density functional methods in calculating and describing the vibrational frequencies of benzene was determined. Different levels were used. The modes were characterized by the magnitude and direction of the displacement vector. The error in the calculated frequencies was reduced using two procedures to obtain the scaled frequencies. Scaling equations were determined for each theoretical method. Specific scale factors were calculated to reduce the error in the ring modes of benzene derivatives.

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Hartree-Fock calculation of the harmonic force constants and equilibrium geometry of formaldehyde

Cited by 92 publications

References 34 publications

Calculation of harmonic force constants by semiempirical methods

Calculation of harmonic force constants by semiempirical methods

Scaling factors for the prediction of vibrational spectra. II. The aniline molecule and several derivatives

Scaling factors for the prediction of vibrational spectra. I. Benzene molecule

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