A CASSCF/CASPT2 STUDY ON THE LOW-LYING ELECTRONIC STATES OF THE (CH3)2CHS AND ITS CATION

2013 ◽  
Vol 12 (06) ◽  
pp. 1350047
Author(s):  
FAN-XIA WANG ◽  
ZENG-XIA ZHAO ◽  
HONG-XING ZHANG
Keyword(s):  
Ground State ◽  
Spectroscopic Data ◽  
Geometry Optimization ◽  
Electronic States ◽  
Vibrational Frequencies ◽  
Geometric Parameters ◽  
Basis Set ◽  
Natural Orbital ◽  
Atomic Natural Orbital ◽  
Good Agreement

The multireference approach (CASSCF/CASPT2) combined with the contracted with atomic natural orbital (ANO-RCC-VTZP) basis set has been used to investigate systematically, the low-lying electronic states of ( CH 3)2 CHS in Cs symmetry. The result of geometry optimization using CASSCF/ANO-RCC-VTZP shows that the theoretically determined geometric parameters and harmonic vibrational frequencies for the ground state X2A′ of ( CH 3)2 CHS are in good agreement with previous studies. In addition, we also explored several cationic states adiabatically and found that the 11A′ state of ( CH 3)2 CHS + is unstable and converts to ( CH 3)2 CSH +. The vertical and adiabatic ionization energies were obtained to compare with photoelectron spectroscopic data.

The Ground State Potential for the Chromium Dimer Revisited

2003 ◽  
Vol 68 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Björn O. Roos
Keyword(s):  
Ground State ◽  
Theoretical Study ◽  
Relativistic Effects ◽  
Basis Set ◽  
Spectroscopic Constants ◽  
Natural Orbital ◽  
State Potential ◽  
Experimental Values ◽  
Atomic Natural Orbital ◽  
Caspt2 Calculations

Results are presented from a new theoretical study of the ground state potential curve of the chromium dimer using multiconfiguration second-order perturbation theory. A new basis set of the atomic natural orbital type is used where the construction includes correlation of the semi-core 3p orbitals and scalar relativistic effects are added using the Douglas-Kroll Hamiltonian. The active space used in the CASSCF/CASPT2 calculations comprised 16 orbitals with 12 active electrons. The resulting ground state potential is in agreement with experiment. Computed spectroscopic constants are (with experimental values within parentheses): Re = 1.66 (1.68) Å, D0 = 1.65 (1.53 ± 0.06) eV, ∆G1/2 = 413 (452) cm-1. Higher vibrational frequencies are also well reproduced.

Ab initio studies on amides: conformational preferences of formimide and barriers to interconversion of the conformers

1980 ◽  
Vol 33 (8) ◽  
pp. 1635 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Ground State ◽  
Room Temperature ◽  
Geometry Optimization ◽  
Basis Set ◽  
Partial Geometry ◽  
Electrostatic Repulsion ◽  
Full Geometry Optimization ◽  
Vapour State ◽  
Conformational Preferences ◽  
Model Transition

Formimide (diformamide), the parent of the diacylamines, is capable of existing in three basic ground-state conformations about the N-C bonds. Full geometry optimization with the STO-3G basis set predicts that all three conformers are fully coplanar, that the E,E (1) and E,Z(3) conformers are of similar energy, and that the Z,Z (2) conformer is of somewhat higher energy (by 11 kJ mol-1); 4-31G evaluation of the energies suggests that (2) is by far the least stable and that (1) is of higher energy than (3) by 6.5 kJ mol-1. Analysis of the calculated charge distribution suggests that (2) is destabilized by electrostatic repulsion. These results are consistent with experimental conclusions that planar (3) is strongly preferred in the vapour state at room temperature and that (2) has not been observed in the vapour state or in solution. Partial geometry optimization with the STO-3G basis set of model transition states for internal rotation suggests a barrier height of 52 kJ mol-1 (72 kJ mol-1 when evaluated with the 4-31G basis set) for the conversion (3) → (1).

scholarly journals Density Functional Theory Study on Conformers of Benzoylcholine Chloride

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Mustafa Karakaya ◽  
Fatih Ucun ◽  
Ahmet Tokatlı
Keyword(s):  
Density Functional Theory ◽  
Ground State ◽  
Density Functional ◽  
Atomic Orbital ◽  
Nbo Analysis ◽  
Vibrational Frequencies ◽  
Molecular Structures ◽  
Basis Set ◽  
Functional Theory ◽  
B3lyp Method

The optimized molecular structures and vibrational frequencies and also gauge including atomic orbital (GIAO)1H and13C NMR shift values of benzoylcholine chloride [(2-benzoyloxyethyl) trimethyl ammonium chloride] have been calculated using density functional theory (B3LYP) method with 6-31++G(d) basis set. The comparison of the experimental and calculated infrared (IR), Raman, and nuclear magnetic resonance (NMR) spectra has indicated that the experimental spectra are formed from the superposition of the spectra of two lowest energy conformers of the compound. So, it was concluded that the compound simultaneously exists in two optimized conformers in the ground state. Also the natural bond orbital (NBO) analysis has supported the simultaneous exiting of two conformers in the ground state. The calculated optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies for both the lowest energy conformers were seen to be in a well agreement with the corresponding experimental data.

scholarly journals Spectroscopic Investigations and DFT Calculations on 3-(Diacetylamino)-2-ethyl-3H-quinazolin-4-one

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Yusuf Sert ◽  
Fatih Ucun ◽  
Gamal A. El-Hiti ◽  
Keith Smith ◽  
Amany S. Hegazy
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Solid Phase ◽  
Vibrational Frequencies ◽  
Geometric Parameters ◽  
Basis Set ◽  
Potential Energy Distribution ◽  
Laser Raman ◽  
Quantum Chemical Methods ◽  
Lowest Unoccupied Molecular Orbital

The theoretical and experimental vibrational frequencies of 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) were investigated. The experimental Laser-Raman spectrum (4000–100 cm−1) and FT-IR spectrum (4000–400 cm−1) of the newly synthesized compound were recorded in the solid phase. Both the theoretical vibrational frequencies and the optimized geometric parameters such as bond lengths and bond angles have for the first time been calculated using density functional theory (DFT/B3LYP and DFT/M06-2X) quantum chemical methods with the 6-311++G(d,p) basis set using Gaussian 03 software. The vibrational frequencies were assigned with the help of potential energy distribution (PED) analysis using VEDA 4 software. The calculated vibrational frequencies and the optimized geometric parameters were found to be in good agreement with the corresponding reported experimental data. Also, the energies of the lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital (HOMO), and other related molecular energies for 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) have been investigated using the same computational methods.

Abinitio Calculations of the Barriers to Rotation in Some Monosubstituted Benzenes

1986 ◽  
Vol 39 (7) ◽  
pp. 1157 ◽  
Author(s):  
S Marriott ◽  
RD Topsom
Keyword(s):  
Electron Transfer ◽  
Ab Initio ◽  
Benzene Ring ◽  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Basis Set ◽  
Monosubstituted Benzenes ◽  
Split Valence ◽  
Good Agreement ◽  
Abinitio Calculations

Theoretical calculations at the ab initio level have been made of the twofold rotational barriers of some monosubstituted benzenes, and the effects both of basis set and of geometry optimization have been examined. Values at the STO-3G//STO-3G level are in good agreement with experiment. The use of split-valence sets, even with geometry optimization, is much less satisfactory, and this may be related to an overestimation of π-electron transfer between the substituent and the benzene ring.

Theoretical calculation of the low-lying quartet states of the CrF molecule

2011 ◽  
Vol 89 (10) ◽  
pp. 1304-1311 ◽  
Author(s):  
A. Hamdan ◽  
M. Korek
Keyword(s):  
Dipole Moment ◽  
Potential Energy ◽  
Ground State ◽  
Electronic States ◽  
Rotational Constant ◽  
Electronic Energy ◽  
Harmonic Frequency ◽  
First Time ◽  
Theoretical Results ◽  
Good Agreement

The potential energy curves have been investigated for the 11 lowest quartet electronic states in the 2s+1Λ± representation below 28 000 cm–1 of the molecule CrF via CASSCF and MRCI (single and double excitations with Davidson correction) calculations. Eight electronic states have been studied theoretically for the first time. The harmonic frequency ωe, the internuclear distance re, the rotational constant Be, the electronic energy with respect to the ground state Te, and the permanent dipole moment μ have been calculated. By using the canonical functions approach, the eigenvalues Ev, the rotational constant Bv, and the abscissas of the turning points rmin and rmax have been calculated for electronic states up to the vibrational level v = 38. The comparison of these values to the theoretical results available in the literature shows a very good agreement.

scholarly journals Theoretical Studies of Structure, Spectroscopy, and Properties of a New Hydrazine Derivative

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Hajar Sahebalzamani ◽  
Farshid Salimi ◽  
Elmira Dornapour
Keyword(s):  
Ground State ◽  
Theoretical Study ◽  
Molecular Geometry ◽  
Vibrational Frequencies ◽  
Basis Sets ◽  
Theoretical Studies ◽  
Hydrazine Derivative ◽  
Homo And Lumo ◽  
Good Agreement ◽  
Ft Raman

We will report a combined experimental and theoretical study on molecular structure, vibrational spectra, and energies of (E)-1-(2,4-dinitrophenyl)-2-[(4-methylphenyl)methylidene]hydrazine (1). The molecular geometry and vibrational frequencies and energies in the ground state are calculated by using HF and DFT levels of theory with 6-311G basis sets. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. The harmonic vibrational frequencies were calculated, and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar-type spectrograms.

Sign in / Sign up

Export Citation Format

Share Document