Theoretical studies on the absorption and luminescent properties of a series of derivatives of 1,3-diphenyl-5-pyrene-2-yl-4,5-dihydro-1H-pyrazole

2005 ◽  
Vol 83 (2) ◽  
pp. 166-173 ◽  
Author(s):  
Xiao-Juan Liu ◽  
Ji-Kang Feng ◽  
Ai-Min Ren ◽  
Xin Zhou ◽  
Hong Cheng
Keyword(s):  
Ground State ◽  
Emission Spectra ◽  
Luminescent Properties ◽  
Basis Set ◽  
Basis Sets ◽  
Absorption And Emission ◽  
Reaction Field ◽  
Hartree Fock ◽  
Polarized Continuum Model ◽  
Experimental Values

The absorption and emission spectra for a series of substituted 1,3-diphenyl-5-pyrene-2-yl-4,5-dihydro-1H-pyrazole (DPPyP) molecules are computed by TDDFT methods. The solvent effect is modeled using the self-consistent reaction field (SCRF) method with Tomasi's polarized continuum model (PCM). The ground-state geometries were optimized by the Hartree–Fock method with the 6-31G basis set (and also with 3-21G* for molecule A) (HF/6-31G), and the lowest singlet excited-state geometries were optimized at the ab initio CIS level with the 6-31G basis set (CIS/6-31G). The calculated results indicate that the TDDFT method can reproduce the experimental values. We consider the effects of different basis sets on the optimization of the ground-state geometries. Specially, some insights on the differences observed for these compounds in changing the substituted donors (H, CH3, and NH2) and acceptor group (CN) are given; the results indicate that introduction of the donor groups will lead emission to be red-shifted, while introduction of the acceptor will induce the emission to be blue-shifted, which provides useful information for modulating light-emitting material colors.Key words: absorption and emission, TDDFT, CIS, SCRF–PCM.

The simplified ab initio method calculation of linear polarizability

1973 ◽  
Vol 26 (5) ◽  
pp. 921 ◽  
Author(s):  
RD Brown ◽  
GR Williams
Keyword(s):  
Ab Initio ◽  
Small Molecules ◽  
Basis Set ◽  
Basis Sets ◽  
Orbital Method ◽  
Polarizability Anisotropy ◽  
Minimal Basis ◽  
Hartree Fock ◽  
Numerical Performance ◽  
Experimental Values

The simplified ab-initio molecular-orbital method described previously is particularly suited to the calculation of polarizabilities by the non-perturbative coupled Hartree-Fock technique. Trial calculations on CO and HF, for which comparison with corresponding ab-initio calculations is possible, show that the method gives an adequate numerical performance. Minimal basis set calculations in general tend to give values that are considerably too low because of inadequate flexibility of the basis and this is the origin of the large discrepancy between theory and experiment, especially for small molecules. ��� Results are also reported for N2O and O3. For these larger systems the SAI results with minimal basis sets are noticeably nearer experimental values. The polarizability anisotropy for N2O is particularly well reproduced by the SAI method. �

Studies on the Effectes of XC Functionals and Basis Sets on the Geometrical Structures, Absorption and Emission Spectra of a 1,8-naphthalimide Derivative

2014 ◽  
Vol 904 ◽  
pp. 195-199
Author(s):  
Yuan Fang Hu ◽  
Guang Hua Nie
Keyword(s):  
Density Functional ◽  
Emission Spectra ◽  
Electron Transition ◽  
Basis Set ◽  
Basis Sets ◽  
Property A ◽  
Geometrical Structures ◽  
Transition Energies ◽  
Absorption And Emission ◽  
Polarizable Continuum

N-Hexyl-4-(thiophen-2-yl)-1,8-naphthalimide (HTNI) is one of the 1,8-naphthalimide derivatives with excellent fluorescence property. A scheme of time-dependent density functional theory (TDDFT) and configuration interaction singles (CIS) approach in conjunction with polarizable continuum models (PCMs) are employed to make a detailed investigation of the emitting energy. The transition energies of absorption and emission are computed using five exchange-correlation (XC) functionals, B3LYP, PBE0, M06, CAM-B3LYP, and wB97XD as well as 6-31G* and 6-31+G* basis sets. The results show that the predicted emitting energies as well as the absorption ones are dominated mainly by XC functional to be used. By comparing the calculated electron transition energies to experimental observations, it is found that PBE0 functional in combination with 6-31G* basis set is the best method to reproduce the experimental spectra of HTNI.

CHARACTERIZATION OF THE $\tilde{X}\,^2 \Pi$ AND Ã2Σ+ ELECTRONIC STATES OF THE PHOSPHAETHYNE CATION (HCP+)

2005 ◽  
Vol 04 (spec01) ◽  
pp. 707-724 ◽  
Author(s):  
BERHANE TEMELSO ◽  
NANCY A. RICHARDSON ◽  
LEVENT SARI ◽  
YUKIO YAMAGUCHI ◽  
HENRY F. SCHAEFER
Keyword(s):  
Ground State ◽  
Dipole Moments ◽  
Basis Set ◽  
Basis Sets ◽  
Structure Theory ◽  
Coupled Cluster ◽  
Excitation Energies ◽  
State Formula ◽  
Correlation Consistent ◽  
Experimental Values

The electronic ground state [Formula: see text] and first excited state (Ã2Σ+) of phosphaethyne cation (HCP+) have been systematically investigated using ab initio electronic structure theory. The total energies, geometries, rotational constants, dipole moments, harmonic vibrational frequencies, and parameters for Renner–Teller splittings were determined using self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), coupled cluster (CC) with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], CC with single, double, and iterative partial triple excitations (CCSDT-3), and CC with single, double, and full triple excitations (CCSDT) methods and eight different basis sets. Some of the largest full triples coupled cluster computations to date are reported. Degenerate bending frequencies for the Ã2Σ+ state were determined using the equation-of-motion (EOM)-CCSD technique. The two states have been confirmed to have linear equilibrium structures. At the full CCSDT level of theory with the correlation-consistent polarized valence quadruple zeta (cc-pVQZ) basis set, the classical [Formula: see text] splitting ( T e value) is predicted to be 47.7 kcal/mol (2.07 eV, 16,700 cm-1) and the quantum mechanical splitting (T0 value) to be 48.1 kcal/mol (2.08 eV, 16,800 cm-1), which are in excellent agreement with the experimental values of T e = 47.77 kcal/mol (2.072 eV , 16,708 cm -1) and T0 = 47.94 kcal/mol (2.079 eV, 16,766 cm-1). The excitation energies predicted by the CCSDT-3 and CCSD(T) methods differ from the full triples CCSDT result by 0.38 and 0.45 kcal/mol, respectively. With the aug-cc-pVQZ CCSDT-3 method the Renner parameter and the averaged harmonic bending vibrational frequency are determined to be ∊= -0.0390 and [Formula: see text] for the ground state of HCP+, which are reasonably consistent with the experimental values of ∊=-0.0415 and [Formula: see text]. The predicted dipole moments are 1.30 Debye ([Formula: see text] state, polarity-hydrogen atom positive) and 0.06 Debye (Ã2Σ+ state, polarity-phosphorus atom positive).

DFT Benchmark Study of the O--O Bond Dissociation Energy in Peroxides Validated with High-Level Ab-Initio Calculations

2019 ◽  
Author(s):  
Danilo Carmona ◽  
Pablo Jaque ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Reference Value ◽  
Basis Set ◽  
Basis Sets ◽  
Mean Deviation ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
The Mean ◽  
Experimental Values ◽  
High Level ◽  
Almost All

<div><div><div><p>Peroxides play a central role in many chemical and biological pro- cesses such as the Fenton reaction. The relevance of these compounds lies in the low stability of the O–O bond which upon dissociation results in radical species able to initiate various chemical or biological processes. In this work, a set of 64 DFT functional-basis set combinations has been validated in terms of their capability to describe bond dissociation energies (BDE) for the O–O bond in a database of 14 ROOH peroxides for which experimental values ofBDE are available. Moreover, the electronic contributions to the BDE were obtained for four of the peroxides and the anion H2O2− at the CBS limit at CCSD(T) level with Dunning’s basis sets up to triple–ζ quality provid- ing a reference value for the hydrogen peroxide anion as a model. Almost all the functionals considered here yielded mean absolute deviations around 5.0 kcal mol−1. The smallest values were observed for the ωB97 family and the Minnesota M11 functional with a marked basis set dependence. Despite the mean deviation, order relations among BDE experimental values of peroxides were also considered. The ωB97 family was able to reproduce the relations correctly whereas other functionals presented a marked dependence on the chemical nature of the R group. Interestingly, M11 functional did not show a very good agreement with the established order despite its good performance in the mean error. The obtained results support the use of similar validation strategies for proper prediction of BDE or other molecular properties by DF Tmethods in subsequent related studies.</p></div></div></div>

Gaussian basis sets for the atoms from K through Xe

2001 ◽  
Vol 79 (2) ◽  
pp. 121-123 ◽  
Author(s):  
R Centoducatte ◽  
E VR de Castro ◽  
F E Jorge
Keyword(s):  
Key Words ◽  
Ground State ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Generator Coordinate ◽  
Discretization Technique ◽  
Total Energies

An improved generator coordinate Hartree-Fock (IGCHF) method is used to generate Gaussian basis sets for the atoms from K (Z = 19) through Xe (Z = 54). The Griffin-Hill-Wheeler-HF equations are integrated using the integral discretization technique. The ground state HF total energies obtained by us are compared with those calculated with the original GCHF method and with other approaches reported in the literature. The largest difference between our energy values and the corresponding ones computed with a numerical HF method is equal to 6.003 mhartree for Kr (Z = 36).Key words: improved generator coordinate Hartree-Fock method, Gaussian basis sets, total energies.

Accuracy Assessment of the ROHF-CCSD(T) Calculationsof Dipole Moments of Small Radicals

1998 ◽  
Vol 63 (9) ◽  
pp. 1409-1430 ◽  
Author(s):  
Miroslav Urban ◽  
Pavel Neogrády ◽  
Juraj Raab ◽  
Geerd H. F. Diercksen
Keyword(s):  
Large Deviation ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Accuracy Assessment ◽  
Open Shell ◽  
Basis Set ◽  
Coupled Cluster ◽  
Hartree Fock ◽  
Experimental Values

Dipole moments of a series of radicals, OH, NO, NS, SF, SO, PO, ClO, CN, LiO, NO2, and ClO2 were calculated by the Coupled Cluster CCSD(T) method with the single determinant restricted open shell Hartree-Fock (ROHF) reference. For all molecules theoretical dipole moments were carefully compared to experimental values. The size and the quality of the basis set were systematically improved. Spin adaptation in the ROHF-CCSD(T) method, largest single and double excitation amplitudes and the T1 diagnostics were considered as indicators in the quality assessment of calculated dipole moments. For most molecules the accuracy within 0.01-0.03 D was readily obtained. For ClO and CN the spin adaptation was necessary - its contribution was as large as 0.03-0.045 D. Large deviation from experiment is observed for OH in its A2Σ+ excited state (0.135 D) and especially for LiO in its 2Π ground state (0.22 D). No indication of the failure of theoretical calculations was found which leads to the conclusion that, even if there is still a space for the improvement of theoretical calculations, experimental values should be reconsidered.

scholarly journals Accurate global potential energy surface for the ground state of CH2+ by extrapolation to the complete basis set limit

RSC Advances ◽  
2018 ◽  
Vol 8 (25) ◽  
pp. 13635-13642 ◽  
Author(s):  
Lu Guo ◽  
Hongyu Ma ◽  
Lulu Zhang ◽  
Yuzhi Song ◽  
Yongqing Li
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ground State ◽  
Energy Surface ◽  
Correlation Energy ◽  
Basis Set ◽  
Basis Sets ◽  
Complete Basis ◽  
Complete Basis Set ◽  
Complete Basis Set Limit

A full three-dimensional global potential energy surface is reported for the ground state of CH2+ by fitting accurate multireference configuration interaction energies calculated using aug-cc-pVQZ and aug-cc-pV5Z basis sets with extrapolation of the electron correlation energy to the complete basis set limit.

Intermolecular Effects on Third Order Nonlinear Optical Properties

1992 ◽  
Vol 247 ◽  
Author(s):  
D. S. Dudis ◽  
A. T. Yeates ◽  
H. A. Kurtz
Keyword(s):  
Optical Properties ◽  
Intermolecular Interactions ◽  
Nonlinear Optical ◽  
Basis Set ◽  
Basis Sets ◽  
Intermolecular Potential ◽  
Correlation Effects ◽  
Third Order ◽  
Hartree Fock ◽  
Intermolecular Contacts

ABSTRACTHartree-Fock ab initio calculations have been used to examine the magnitude of non-polar intermolecular interactions on polarizabilities and second hyperpolarizabilities. In the present case two ethylene molecules were examined in a cofacial interaction. Basis set requirements and correlation effects were considered in deriving the intermolecular potential. Two basis sets were considered for the intermolecular interactions at the Hartree-Fock level, while one set of calculations was performed with corrections for correlation. It is found that intermolecular contacts at the van der Waals distance has little effect on the molecular second hyperpolarizability, but it is not clear what the effect would be for longer oligomers.

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