The infrared spectrum of 2-methylaziridine from scaled abinitio force fields

1992 ◽  
Vol 70 (2) ◽  
pp. 464-477 ◽  
Author(s):  
Arvi Rauk ◽  
T. Eggimann ◽  
H. Wieser ◽  
Danya Yang
Keyword(s):  
Infrared Spectrum ◽  
Vapor Phase ◽  
Ir Spectrum ◽  
Force Fields ◽  
Experimental Spectrum ◽  
Equilibrium Mixture ◽  
Basis Set ◽  
Complete Assignment ◽  
Cis And Trans ◽  
Good Agreement

The structures of the cis and trans invertomers of 2-methylazirdine were optimized at the RHF/6-31G*(0.3) level of theory and the composition of the equilibrium mixture was determined to be trans/cis = 0.71:0.29, in good agreement with the experimental value, 0.66:0.35. The abinitio force field was scaled and a complete assignment of the vibrational spectra of the two conformers is presented. The IR spectrum of 2-methylazirdine was recorded in the vapor phase and in solution (cyclohexane and CCl4). The predicted IR spectrum of the equilibrium mixture agrees very well with the experimental spectrum. The 6-31G*(0.3) basis set is found to provide better geometries and more uniformly scalable force fields than the conventional 6-31G* basis set. Keywords: abinitio force fields, 2-methylaziridine.

The vibrational circular dichroism spectra of 2-methylaziridine: dominance of the asymmetric centre at nitrogen

1994 ◽  
Vol 72 (3) ◽  
pp. 506-513 ◽  
Author(s):  
Arvi Rauk ◽  
Thomas Eggimann ◽  
Helmut Wieser ◽  
Gennadii V. Shustov ◽  
Danya Yang
Keyword(s):  
Equilibrium Mixture ◽  
Vibrational Circular Dichroism ◽  
Basis Set ◽  
Quantum Mechanical ◽  
Coupling Theory ◽  
Similar Magnitude ◽  
Chiroptical Properties ◽  
Methyl Group ◽  
The Common ◽  
Cis And Trans

The experimental VCD spectrum of (2R)-2-methylaziridine has been measured in the region 800–1500 cm−1. The ab initio implementation of the Vibronic Coupling Theory (VCT) of Nafie and Freedman, using the 6-31G*(0.3) basis set, in the common origin and distributed origin gauges and with uniformly and optimally scaled quantum mechanical force fields, is used to investigate the chiroptical properties. VCD spectra are computed for both cis and trans invertomers. The predicted VCD spectrum of 2-methylaziridine (the equilibrium mixture) is dominated by that of the trans diastereomer, not simply because of its greater abundance but because the rotatory strengths of many absorptions in the mid-IR are oppositely signed and of similar magnitude in the two invertomers which differ in absolute configuration at nitrogen. The VCD spectrum of 2-methylaziridine is compared in detail to that of 2-methyloxirane. In the region of the methyl group deformations and CH2 scissor, the theoretical (R)-2-methyloxirane VCD spectrum displays a much closer similarity to the cis-(2R)-2-methylaziridine than to the trans diastereomer.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

scholarly journals Experimental and Theoretical Study of the Enthalpy of Formation of 3,6-Diphenyl-1,2,4,5-Tetroxane Molecule

2002 ◽  
Vol 2 ◽  
pp. 455-460 ◽  
Author(s):  
N.L. Jorge ◽  
L.C.A. Leiva ◽  
M.G. Castellanos ◽  
M.E. Gomez Vara ◽  
L.F.R. Cafferata ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Enthalpy Of Formation ◽  
Vapor Phase ◽  
Theoretical Study ◽  
Theoretical Calculations ◽  
Basis Set ◽  
Sublimation Enthalpy ◽  
Combustion Heat ◽  
Different Temperatures ◽  
The Enthalpy Of Formation

We report the results obtained for the experimental determination and the theoretical calculation of the enthalpy of formation of 3,6-diphenyl-1,2,4,5-tetroxane molecule. The experimental work was performed using a macrocalorimeter to measure the combustion heat, and the sublimation enthalpy was determined via the measurement of the vapor pressure at equilibrium with the vapor phase at different temperatures resorting to the Clapeyron-Claussius equation. Theoretical calculations were performed using semiempirical AM1 and PM3 methods as well asab initiotechniques at the 3-21, 6-31G(d,p), and 6-311G(d,p) basis set levels.

scholarly journals Изотопные эффекты в спектрах комплексов с водородными связями. Ангармонические расчеты изотопологов комплекса [F(HF)-=SUB=-2-=/SUB=-]-=SUP=---=/SUP=-

2020 ◽  
Vol 128 (8) ◽  
pp. 1077
Author(s):  
В.П. Булычев ◽  
М.В. Бутурлимова ◽  
К.Г. Тохадзе
Keyword(s):  
Basis Set ◽  
Ir Absorption ◽  
Absorption Bands ◽  
Spectral Parameters ◽  
Basis Set Superposition Error ◽  
Band Frequency ◽  
Normal Vibrations ◽  
K Meson ◽  
Anharmonic Interactions ◽  
Good Agreement

The frequencies and intensities of IR absorption bands of symmetric and asymmetric H-bonded complexes [FL1FL2F]- (L1, L2 = K-meson Ka, proton H, deuton D, and triton T) are calculated. The equilibrium configuration and potential energy and dipole moment surfaces of isotopologues [FL1FL2F]- were calculated by the MP2/6-311++G(3df,3pd) method with the basis set superposition error taken into account. The calculations of spectral parameters with allowance for anharmonic interactions of all vibrations were carried out using the second-order vibrational perturbation theory. Variation of Li and L2 masses in wide regions allowed significant changes in the forms of normal vibrations and values of anharmonic interaction constants upon isotopic substitution to be obtained. The trends in the changes of spectral parameters were determined upon transition from one symmetric isotopologue to another and upon transition from symmetric to asymmetric isotopologues. The D-F stretching band frequency predicted for [FHFDF]- is in good agreement with the experimental value. The assignment of this band was improved.

Notizen: Das Infrarotspektrum des Tetraselentetranitrids, Se4N4 / The Infrared Spectrum of Tetraseleniumtetranitride, Se4N4

1988 ◽  
Vol 43 (5) ◽  
pp. 639-640 ◽  
Author(s):  
Jörg Adel ◽  
Christina Ergezinger ◽  
Reiner Figge ◽  
Kurt Dehnicke
Keyword(s):  
Infrared Spectrum ◽  
Structure Determination ◽  
Ir Spectrum ◽  
X Ray

Abstract The IR spectrum of solid Se4N4 has been recorded in the region of 100- 4000 cm-1 . The assignment has been made on the basis of slightly deformed D2d symmetry, which is in agreement with the X-ray structure determination.

Conformational Structure of Chloromethyldichlorophosphines

2002 ◽  
Vol 57 (6-7) ◽  
pp. 333-336
Author(s):  
Evgenii A. Romanenko ◽  
Alexander M. Nesterenko
Keyword(s):  
Experimental Data ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Conformational Structure ◽  
Gauche Conformation ◽  
Nuclear Quadrupole ◽  
Set Up ◽  
Good Agreement

IThe 35Cl nuclear quadrupole resonances (77 K) and ab initio calculations of trichloromethyldichlorophosphine () show that it exists in the chess conformation form. The barrier to internal rotation about the P-C bond in I at the RHF/6-31++ G(d,p) level equals to 38.1 kJ mol-1. In chloromethyldichlorophosphine (II) the extension of the basis set up to the RHF/6-311++G(df, pd) level does not improve the description of the most preferable gauche-conformation; only if electron correlation (at the MP2 level) is taken into account the results are in a good agreement with experimental data.

Universal Gaussian basis functions in relativistic quantum chemistry: atomic Dirac–Fock–Coulomb and Dirac–Fock–Breit calculations

1992 ◽  
Vol 70 (6) ◽  
pp. 1822-1826 ◽  
Author(s):  
G. L. Malli ◽  
A. B. F. Da Silva ◽  
Yasuyuki Ishikawa
Keyword(s):  
Relativistic Quantum ◽  
Basis Set ◽  
Basis Sets ◽  
Interaction Energies ◽  
Gaussian Basis Sets ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Gaussian Basis Set ◽  
Good Agreement

Matrix Dirac–Fock–Coulomb and Dirac–Fock–Breit self-consistent field calculations are performed for a number of neutral atoms. He (Z = 2) through Xe (Z = 54), using the universal Gaussian basis set (18s, 12p, 11d) reported recently by Da Silva etal. The total Dirac–Fock–Coulomb, the Dirac–Fock–Breit, and the Breit interaction energies calculated with this universal Gaussian basis set are in good agreement with the corresponding values obtained by using an extensive well-tempered Gaussian basis set for the He through Ca (Z = 20) atoms. Although this universal Gaussian basis set is inadequate for the calculation of total Dirac–Fock–Coulomb and Dirac–Fock–Breit energies for the Kr, Sr, and Xe atoms, the Breit interaction energies calculated with this basis for these three atoms are in very good agreement with the corresponding Breit interaction energies obtained by using the extensive well-tempered Gaussian basis sets. Work is in progress to generate a more extensive and energetically better universal Gaussian basis set for He through Xe for its use in non-relativistic Hartree–Fock as well as Dirac–Fock self-consistent field calculations on polyatomics involving heavy atoms.

Tests of second-generation and third-generation density functionals for electron affinities of the alkylthio radicals

2014 ◽  
Vol 13 (04) ◽  
pp. 1450030 ◽  
Author(s):  
Aifang Gao ◽  
Aiguo Li
Keyword(s):  
Dft Method ◽  
Absolute Error ◽  
Molecular Structures ◽  
Basis Set ◽  
Density Functionals ◽  
Electron Affinities ◽  
Generalized Gradient ◽  
Experimental Values ◽  
P Type ◽  
Good Agreement

The molecular structures and electron affinities of the R – S / R – S -( R = CH 3, C 2 H 5, n- C 3 H 7, n- C 4 H 9, n- C 5 H 11, i- C 3 H 7, i- C 4 H 9, t- C 4 H 9) species have been studied using 17 pure and hybrid density functionals (five generalized gradient approximation (GGA) methods, six hybrid GGAs, one meta GGA method and five hybrid meta GGAs). The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted by DZP++. The geometries are fully optimized with each DFT method and discussed. Harmonic vibrational frequencies are found to be within 3.5% of available experimental values for most functionals. Three different types of the neutral-anion energy separations have been presented. The theoretical electron affinities of alkylthio radicals are in good agreement with the experiment data. The M06 method is very good for the adiabatic electron affinity calculations, and the average absolute error is 0.0439 eV. The HCTH method performs better for EA prediction. The M06-HF, mPWPW91, VSXC and B98 are also reasonable. The most reliable adiabatic electron affinities are predicted to be 1.864 eV ( CH 3 S ), 1.946 eV ( C 2 H 5 S ), 1.959 eV (n- C 3 H 7 S ), 1.970 eV (n- C 4 H 9 S ), 1.982 eV (n- C 5 H 11 S ), 2.053 eV (i- C 3 H 7 S ), 1.991 eV (i- C 4 H 9 S ) and 2.100 eV (t- C 4 H 9 S ) at the M06/DZP++ level of theory, respectively.

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