Theoretical studies on ClOO — electronic spectra, ionization potential, and electron affinity

2011 ◽  
Vol 89 (8) ◽  
pp. 891-897 ◽  
Author(s):  
Friedrich Grein
Keyword(s):  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Oscillator Strengths ◽  
Electron Affinities ◽  
Excitation Energies ◽  
Vertical Excitation ◽  
Avoided Crossings ◽  
Cluster Methods ◽  
Configuration Interaction Calculations

Vertical excitation energies and oscillator strengths of doublet and quartet states of ClOO, covering doublet states up to 7.5 eV and quartet states up to 9 eV, were obtained by multireference configuration interaction calculations. Strong absorptions from the X2A″ ground state are predicted at 186 and 235 nm. Experimentally, a maximum has been found near 248 nm. The grouping of excited states, with twelve low-lying doublet states and three low-lying quartet states, is explained by the interaction of the 2P ground state of Cl with the π*2 states 3Σg–, 1Δg, and 1Σg+ of O2. Potential energy curves for Cl–O separation at fixed O–O distance and ClOO angle show the lower states to be repulsive (with the exception of the ground state), and higher states to have minima due to avoided crossings. The lowest Rydberg states are expected around 8.5 eV. Adiabatic ionization potentials (IP) and electron affinities (EA) of ClOO were obtained by density functional and coupled cluster methods, with values of 11.60–11.79 eV for IP and 3.56–3.79 eV for EA.

The ground state and low-lying excited states of CCCN radical and its ions: a CASSCF/CASPT2 study

2016 ◽  
Vol 94 (9) ◽  
pp. 803-807
Author(s):  
Angyang Yu
Keyword(s):  
Excited States ◽  
Ground State ◽  
Linear Structure ◽  
Electronic Configuration ◽  
Geometric Optimization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Excitation Energies ◽  
Complete Active Space ◽  
Vertical Excitation

The ground state and low-lying excited states of the CCCN radical and its ions have been investigated systematically using the complete active space self-consistent field (CASSCF) and multi-configuration second-order perturbation theory (CASPT2) methods in conjunction with the ANO-RCC-TZP basis set. The calculated results show that the state 12Σ+ has the lowest CASPT2 energy among the electronic states. By means of the geometric optimization of this radical, it could be found that the molecule exhibits linear structure, with the bond lengths R1 = 1.214 Å, R2 = 1.363 Å, R3 = 1.162 Å, which are very close to the experimental values. The calculated vertical excitation energies and the corresponding oscillator strengths show that there are three relatively strong peaks at energies 0.63, 4.04, and 5.49 eV, which correspond to the transitions 12Σ+ → 12Π, 12Σ+ → 22Π, and 12Σ+ → 22Σ+, respectively. Additionally, the electronic configuration and the harmonic vibration frequencies of each state are also investigated.

MR-CISD and MR-AQCC Calculation of Excited States of Malonaldehyde: Geometry Optimizations Using Analytical Energy Gradient Methods and a Systematic Investigation of Reference Configuration Sets

2003 ◽  
Vol 68 (3) ◽  
pp. 447-462 ◽  
Author(s):  
Silmar A. do Monte ◽  
Michal Dallos ◽  
Thomas Müller ◽  
Hans Lischka
Keyword(s):  
Excited States ◽  
Ground State ◽  
Transition Energy ◽  
Gradient Methods ◽  
Systematic Investigation ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Band Maximum ◽  
Vertical Excitation ◽  
Energy Gradient

Extended MR-CISD and MR-AQCC calculations have been performed on the ground state and the first two excited states of malonaldehyde. Full geometry optimizations have been carried for Cs and C2v structures both at MR-CISD and MR-AQCC levels. Vertical and minimum-to-minimum excitation energies and oscillator strengths have been computed. Systematic studies have been undertaken concerning several types of reference spaces. Agreement with the experimental 0-0 transition energy to the S1 state (expt. 3.50 eV, calc. 3.56 eV) and for the vertical excitation to S2 (expt. band maximum 4.71 eV, best estimate 4.86 eV) is very good. In agreement with the CASSCF/CASPT2 results by Sobolewski and Domcke (J. Phys. Chem. A 1999, 103, 4494), we find that the hydrogen bond in malonaldehyde is weakened by excitation to the S1 state. The barrier for proton transfer in the S1 state is increased in comparison with the ground state.

The structure and vertical excitation energies of the chlorothioformyl radical, ClCS: implications for the photofragmentation of thiophosgene

1993 ◽  
Vol 71 (1) ◽  
pp. 112-117 ◽  
Author(s):  
M. Hachey ◽  
F. Grein ◽  
R. P. Steer
Keyword(s):  
Energy Level ◽  
Ab Initio ◽  
Excited States ◽  
Ground State ◽  
Excited Electronic State ◽  
Excitation Energies ◽  
Electronically Excited States ◽  
Vertical Excitation ◽  
Electronically Excited ◽  
Vertical Excitation Energies

Ab initio CI studies have been performed to determine the geometry of the ground and first electronically excited states of the chlorothioformyl radical, ClCS, and the vertical excitation energies of its ten lowest doublet states and two lowest quartet states. The results are used to construct a more complete energy level correlation diagram for the photofragmentation of Cl2CS. The lowest excited electronic state of ClCS lies only 0.79 eV (adiabatic) above the ground state. Its discovery indicates that the results of previous photofragmentation experiments may need to be reinterpreted.

scholarly journals Structural Dependence of Electronic Properties in A-A-D-A-A-Type Organic Solar Cell Material

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Ram S. Bhatta ◽  
Mesfin Tsige
Keyword(s):  
Electronic Properties ◽  
Ground State ◽  
Industrial Development ◽  
Density Functional ◽  
Frontier Molecular Orbital ◽  
Excitation Energies ◽  
Dft Methods ◽  
Potential Surfaces ◽  
Vertical Excitation ◽  
Structural Dependence

Small conjugated molecules (SCMs) are promising candidates for organic photovoltaic (OPV) devices because of their structural simplicity, well control over synthetic reproducibility, and low purification cost. However, industrial development of SCM-based OPV devices requires improving their performance, which in turn relies on the fundamental understanding of structural dependence of electronic properties of SCMs. Herein, we report the structural and electronic properties of the BCNDTS molecule as a model system for acceptor-acceptor-donor-acceptor-acceptor (A-A-D-A-A) type SCMs, using density functional theory (DFT) and time-dependent DFT methods. Systematic calculations of two-dimensional potential energy surfaces, molecular electrostatic potential surfaces, ground state frontier molecular orbital energies, and the vertical excitation energies are performed. We found that the lowest energy conformation of the BCNDTS molecule is planar. The planar conformation favors the lowest ground state and the excited state energies as well as the strongest oscillator strength. The present results suggest that SCMs containing central dithienosilole cores connected with 2,1,3-benzothiadiazole groups have potential to be an efficient electron donor for OPV devices.

DFT/MRCI calculations on the excited states of porphyrin, hydroporphyrins, tetrazaporphyrins and metalloporphyrins

2001 ◽  
Vol 05 (03) ◽  
pp. 225-232 ◽  
Author(s):  
ANDREAS B. J. PARUSEL ◽  
STEFAN GRIMME
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Significant Contribution ◽  
Electronic Absorption Spectra ◽  
Blue Shift ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Functional Theory ◽  
Intense Color ◽  
Higher Excited States

A combination of density functional theory and multi-reference configuration interaction methods (DFT/MRCI) has been applied to the calculation of electronic absorption spectra in a series of porphyrin-type molecules. The calculated excitation energies and oscillator strengths for free-base porphyrin ( PH 2) are in excellent agreement with experiment for both lower and higher excited states which are characterized by a significant contribution of double excitations (>20%). The 41 B 2 u , 41 B 3 u , and 51 B 2 u states are assigned to the L-band and the 71 B 3 u state to the M-band. The results for the hydroporphyrins chlorin ( CH 2) and bacteriochlorin ( BH 2) are in agreement with the experimentally observed increase in intensity for the Q-bands relative to PH 2. For BH 2 we predict a red shift of the Q x -band (0.2 eV) and a blue shift of the B-band (0.5–0.7 eV) in comparison to both PH 2 and CH 2. For porphyrazine ( PzH 2) and the commercial pigment phthalocyanine ( PcH 2) the calculated oscillator strengths of the Q- and B-bands are of comparable size explaining the intense color of PcH 2. For the metalloporphyrins with magnesium ( PMg ) and zinc ( PZn ), the x- and y-polarized components of the Q- and B-bands collapse, due to the higher D4 h symmetry of the molecules. The calculations reproduce the slight, experimentally observed increase in the oscillator strength of the Q-band and the decrease for the B-band. These effects are ascribed to the electropositive nature of the metals relative to hydrogen. Except for the Q-bands, which are adequately described by the 'four-orbital model,' it is essential to account for excitations outside the four frontier orbitals as well as double and triple excitations for accurate reproduction of experimental data. We compare our results both with experiment and, where available, recent first-principle SAC-CI, MRMP, and TDDFT calculations.

scholarly journals Theoretical Investigation on the Electronic and Optical Properties of Poly(fluorenevinylene) Derivatives as Light-Emitting Materials

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Thanisorn Yakhanthip ◽  
Nawee Kungwan ◽  
Jitrayut Jitonnom ◽  
Piched Anuragudom ◽  
Siriporn Jungsuttiwong ◽  
...  
Keyword(s):  
Ground State ◽  
Density Functional ◽  
Time Dependent ◽  
Electron Affinities ◽  
Excitation Energies ◽  
Functional Theory ◽  
Light Emitting ◽  
Long Time ◽  
Maximal Absorption ◽  
Homo Lumo

Density functional theory (DFT) and time-dependent DFT (TDDFT) were employed to study ground-state properties, HOMO-LUMO gaps(ΔH-L), excitation energies(Eg), ionization potentials (IPs), and electron affinities (EA) for PFV-alt-PDONV and PFV-alt-PDIH-PPV having different alternating groups. Excited-state properties were investigated using configuration interaction singles (CISs) while fluorescence energies were calculated using TDDFT. The results show that PFV-alt-PDONV exhibits blue-shifted energies for both HOMO-LUMO gaps(ΔH-L)and excitation energies(Eg)compared with PFV-alt-PDIH-PPV. The predicted IP and EA clearly indicate that PFV-alt-PDIH-PPV has both easier hole creation and electron injection than that of PFV-alt-PDONV. The maximal absorption wavelengths of all polymers are strongly assigned toπ→π∗transition. The predicted radiative lifetimes of PFV-alt-PDONV and PFV-alt-PDIH-PPV for B3LYP/6-31G(d) are 0.36 and 0.61 ns, respectively, indicating that PFV-alt-PDIH-PPV should have a better performance for long-time emission than that of PFV-alt-PDONV.

The calculation of atomic oscillator strengths: the lithium atom revisited

1992 ◽  
Vol 70 (2) ◽  
pp. 456-463 ◽  
Author(s):  
A. W. Weiss
Keyword(s):  
Oscillator Strength ◽  
Excited States ◽  
Configuration Interaction ◽  
Lithium Atom ◽  
Laser Excitation ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Accurate Evaluation ◽  
Theoretical Predictions ◽  
Configuration Interaction Calculations

Extensive configuration interaction calculations have been done for the ground and first excited states of neutral lithium and singly ionized beryllium. While the calculations reproduce the ionization and excitation energies to within 3 cm−1 for Li and 10 cm−1 for Be+, the main purpose of this work is the accurate evaluation of the 2s–2p resonance line oscillator strength. The calculated value of 0.7478 agrees to within less than 1% with the very accurate laser excitation lifetime measurement of 0.7416 ± 0.0012. However, internal consistency checks of the accuracy of these calculations suggest that more precise calculations are unlikely to reduce this discrepancy significantly. Furthermore, when placed together with other independent calculations that should be of comparable, if not better, accuracy, all theoretical predictions strongly indicate an f-value of 0.7475 ± 0.0010, which differs from the experiment by 4 experimental standard deviations. Keywords: configuration interaction, correlation, oscillator strength.

scholarly journals Equilibrium Geometries, Adiabatic Excitation Energies and Intrinsic C=C/C–H Bond Strengths of Ethylene in Lowest Singlet Excited States Described by TDDFT

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1545
Author(s):  
Yunwen Tao ◽  
Linyao Zhang ◽  
Wenli Zou ◽  
Elfi Kraka
Keyword(s):  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Excitation Energies ◽  
Functional Theory ◽  
Local Vibrational Mode ◽  
Strength Change ◽  
Bond Strengths ◽  
First Time ◽  
Equilibrium Geometries

Seventeen singlet excited states of ethylene have been calculated via time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional and the geometries of 11 excited states were optimized successfully. The local vibrational mode theory was employed to examine the intrinsic C=C/C–H bond strengths and their change upon excitation. The natural transition orbital (NTO) analysis was used to further analyze the C=C/C–H bond strength change in excited states versus the ground state. For the first time, three excited states including πy′ → 3s, πy′ → 3py and πy′ → 3pz were identified with stronger C=C ethylene double bonds than in the ground state.

The electronic structure of the first row hydrides BH, CH, NH, OH and FH II. Excited states

1959 ◽  
Vol 249 (1258) ◽  
pp. 402-413 ◽  
Keyword(s):  
Electronic Structure ◽  
Excited States ◽  
Electron Correlation ◽  
Ground States ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Vertical Excitation ◽  
Experimental Values ◽  
Vertical Excitation Energies ◽  
Dipole Length

Previous calculations on the ground states of the hydrides are extended to include the stable excited states. The ab initio orbital calculations predict vertical excitation energies which differ from the experimental values by as much as 2eV. However, when allowance is made for the effects of atomic electron correlation all errors in the calculated excitation energies become less than 0·2eV. The locations of excited states of different multiplicities from those of the ground states are predicted to within this accuracy. The oscillator strengths of allowed transitions from the ground states are calculated using both the dipole-length and dipole-velocity formulae. The dipole-length values are in fair agreement with the only experimental value available (for OH 2 ll → 2 ∑ + ), whereas the dipole-velocity values are much too large. Possible improvements in the accuracy of the calculations are discussed.

Electron density and electrostatic potential-based characteristics of molecular plasmons in polyacenes

2017 ◽  
Author(s):  
Mishu Paul ◽  
Balanarayan Pananghat
Keyword(s):  
Excited States ◽  
Electrostatic Potential ◽  
Ground State ◽  
Density Functional ◽  
Electronic Absorption Spectra ◽  
High Electron ◽  
Excitation Energies ◽  
Electronic Density ◽  
Energy Peak ◽  
Electron Rearrangement

<div>Plasmonic modes in single-molecule systems have been previously identified by scaling two-electron interactions while calculating excitation energies [Bernadotte et al., J. Phys. Chem. C, 2013, <b>117</b>, 1863]. Analysis of transition dipole moments for states of polyacenes based on configuration interaction [Guidez et al., J. Phys. Chem. C, 2013, <b>117</b>, 21466.] was yet another method characterizing molecular plasmons. The principal features in the electronic absorption spectra for polyacenes are a low-intensity, lower-in-energy peak (denoted as α) and a high-intensity, higher-in-energy peak (β ). From our calculations using time-dependent density functional theory (TD-DFT) at B3LYP/cc-pVTZ basis, both the peaks were found to result from the same set of electronic transitions (HOMO-n to LUMO and HOMO to LUMO+n, where n varies as the number of fused rings increases). In this work, the excited states of polyacenes, naphthalene through pentacene, have been analysed using electron densities and molecular electrostatic potential (MESP) topography. The bright and dark plasmonic states involve the least electron rearrangement, as compared to other excited states. Quantitatively, the MESP topography indicates that the variance in MESP values as well as displacement in minima positions (calculated with respect to the ground state) are lowest for plasmonic states. This suggests a resemblance between the plasmonic and ground state electronic density profiles and electrostatic potential topographies. On the other hand, a high electron-rearrangement characterizes a single particle excitation. The molecular plasmon can be called an excited state most similar to the ground state in terms of one-electron properties.</div>

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