The general harmonic force field of formaldehyde
TL;DR: The use of recently available frequency, 13C frequency shift, Coriolis coupling, and centrifugal distortion data enables the GHFF of formaldehyde to be determined with some degree of precision as discussed by the authors.
About: This article is published in Chemical Physics Letters.The article was published on 1973-12-15. It has received 109 citations till now.
Citations
More filters
TL;DR: In this paper, a new version of MOLVIB, a program for vibrational force field calculations, has recently been prepared, which is now possible to perform scale factor calculations according to several methods, which are described.
718 citations
TL;DR: The theory for the analytic evaluation of energy gradients for coupled cluster (CC) wave functions is presented in this paper, where explicit expressions for analytic energy gradient of the CC singles and doubles (CCSD) wave function for a closed-shell restricted Hartree-Fock reference determinant are presented and shown to scale as N6 where N is the one-electron number of atomic basis functions for the molecular system.
Abstract: The theory for the analytic evaluation of energy gradients for coupled cluster (CC) wave functions is presented. In particular, explicit expressions for the analytic energy gradient of the CC singles and doubles (CCSD) wave function for a closed‐shell restricted Hartree–Fock reference determinant are presented and shown to scale as N6 where N is the one‐electron number of atomic basis functions for the molecular system. Thus analytic CCSD gradients are found to be of the same magnitude in computational cost as is the evaluation of analytic gradients for the configuration interaction singles and doubles (CISD) wave function. Applications of this method are presented for the water molecule and the formaldehyde molecule using a double‐ζ plus polarization (DZ+P) basis set. The CCSD equilibrium geometries, dipole moments, and, via finite differences of gradients, CCSD harmonic vibrational frequencies and infrared intensities are reported. For H2O these results are compared to analogous CISD, CISDT, CISDTQ, and...
370 citations
TL;DR: In this paper, a vibrational analysis of the singlet and lower triplet state bands of vinylidene was performed in the ultraviolet (351.1-364.0 nm) photoelectron spectra of X 1A1, a 3B2, and b 3A2 states.
Abstract: The X 1A1, a 3B2, and b 3A2 states of vinylidene are observed in the ultraviolet (351.1–364.0 nm) photoelectron spectra of X 2B2 H2CC−, X 2B2 D2CC−, and X 2A’ HDCC−. The X 1A1 state exhibits vibrational structure well above the barrier for isomerization to acetylene. A strict lower bound to the lifetime of the singlet state against rearrangement is τ>0.027 ps, with an estimate of τ≊0.04–0.2 ps based on a simulation of the line shapes including rotational broadening. A vibrational analysis of the singlet and lower triplet state bands provides vibrational frequencies and estimates of the changes of molecular geometries between the anion and the neutral species. A qualitative potential energy surface for the CH2 rock mode, which closely corresponds to the reaction coordinate for isomerization, is extracted from the experimental data. The adiabatic electron affinity is EA(X 1A1 H2CC)=0.490±0.006 eV and the triplet term energies are T0(a 3B2 H2CC)=2.065±0.006 eV and T0(b 3A2 H2CC)=2.754±0.020 eV. Exp...
343 citations
TL;DR: In this paper, the authors evaluated the performance of analytic third derivative methods for selfconsistent field (SCF) wavefunctions, which have made it possible to determine the complete cubic and quartic force fields of polyatomic molecules, thus allowing the treatment of anharmonic effects.
296 citations
TL;DR: In this paper, the authors evaluated the LDA and LDA/NL schemes on the infrared vibrational frequencies and absorption intensities of H2O, NH3, H2CO, C2H4, CH3OH and oxirane and showed that the calculated frequencies are relatively insensitive to the level of density functional theory as well as to the choice of basis set.
Abstract: Approximate density functional theory has been evaluated as a practical tool for calculations on infrared vibrational frequencies and absorption intensities. The density functional schemes included the local density approximation (LDA) by Gunnarson [Phys. Rev. B 10, 1319 (1974)] as well as a self‐consistent nonlocal density functional method (LDA/NL) in which the gradient corrected exchange term by Becke [Phys. Rev. A 38, 3098 (1988)] and the gradient corrected correlation term by Perdew [Phys. Rev. B 33, 8822 (1986)] has been added to LDA. The LDA and LDA/NL schemes have been applied to calculations on the infrared vibrational frequencies and absorption intensities of H2O, NH3, H2CO, C2H4, CH3OH and oxirane. The calculations were carried out with two basis sets of respectively double‐ζ plus polarization (DZP) and triple‐ζ plus polarization (TZP) quality. The study has demonstrated that vibrational frequencies are relatively insensitive to the level of density functional theory as well as to the choice of basis set. The calculated frequencies are, in general, in better agreement with experiment than values obtained by ab initio Hartree–Fock calculations. Large basis sets of TZP quality are, on the other hand, required for intensities. It is further shown that a small but consistent improvement in the calculated ir intensities is obtained by including nonlocal corrections. The LDA/NL method with a TZP basis set affords ir intensities and frequencies of the same quality as post‐Hartree–Fock methods with an average deviation in the intensities of 20%–40%.
229 citations
References
More filters
TL;DR: In this article, the rotational constants for the isotopic formaldehyde molecules H 2 CO, H 2 C 13 O, D 2 CO and D 3 CO were determined from the parameters used in the analysis of K-type doubling spectra and the frequencies of 1 01 ←0 00 transitions.
Abstract: Rotational constants for the isotopic formaldehyde molecules H 2 CO, H 2 C 13 O, H 2 CO 18 , HDCO and D 2 CO were determined from the parameters used in the analysis of K -type doubling spectra and the frequencies of 1 01 ←0 00 transitions In the cases of isotopic species for which the R -branch transitions were not measured, the calculated inertia defect was used in the determination of the rotational constants From the rotational constants, the zero-point structure of formaldehyde molecule, r z , was determined by a new method taking into account the zero-point vibration-rotation interaction and electronic interaction The following zero-point molecular structure was obtained;
151 citations
TL;DR: In this paper, a brief outline is given of the two principal ways of determining force constants, the method of force constant refinement and force constant display, with particular reference to the assessment of error in the frequency data employed.
80 citations
TL;DR: In this paper, the authors used the vibration-rotation theory for the analysis of the microwave spectrum of formaldehyde molecules and calculated the distortion constants, inertia defects and Coriolis coupling constants.
Abstract: The centrifugal distortion constants and the inertia defects necessary for the analysis of the microwave spectrum of formaldehyde molecule were calculated by the vibration-rotation theory. Nielsen's formulation was used throughout together with the useful relations found by the present authors. The calculated centrifugal distortion constants, inertia defects and Coriolis coupling constants fit well to the experimental values.
63 citations
TL;DR: In this article, microwave spectral lines for the direct transitions between the K -type doublets were measured from 3 kMc to 40 kMc for H 2 CO and for its isotopically substituted molecules HDCO, H 2 C 13 O and H 2 O 18.
Abstract: Microwave spectral lines for the direct transitions between the K -type doublets were measured from 3 kMc to 40 kMc for H 2 CO and for its isotopically substituted molecules HDCO, H 2 C 13 O and H 2 CO 18 . The observed spectra and the previously reported data for H 2 CO were analyzed by a digital computer by the use of Kivelson and Wilson's method for the centrifugal distortion correction. The asymmetry parameter b and B – C were obtained for each isotopic species as follows:
55 citations
TL;DR: In this paper, the rotational constant for the symmetric top approximation was found to be 5.47±0.03 cm −1. This value, combined with the rotations of H2CO obtained by Dieke and Kistiakowsky, yields approximate molecular dimensions for the ground state of formaldehyde.
Abstract: The infrared spectrum of HDCO vapor has been investigated in the region 2.5μ—25μ and all six fundamentals have been observed. Four of the fundamentals have also been observed in the Raman spectrum of the vapor.The perpendicular component of an hybrid band at 3.5μ and the pure rotational Raman spectrum were resolved and analyzed. The rotational constant (A—B) for the symmetric top approximation was found to be 5.47±0.03 cm‐1. This value, combined with the rotational constants of H2CO obtained by Dieke and Kistiakowsky, yields approximate molecular dimensions for the ground state of formaldehyde.
54 citations