scholarly journals NBO/NRT Two-State Theory of Bond-Shift Spectral Excitation

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4052
Author(s):  
Yinchun Jiao ◽  
Frank Weinhold
Keyword(s):  
Ground State ◽  
Density Functional ◽  
Building Blocks ◽  
State Theory ◽  
Alternative Analysis ◽  
Resonance Theory ◽  
Excitation Energies ◽  
Analysis Methods ◽  
Valence Region ◽  
State Models

We show that natural bond orbital (NBO) and natural resonance theory (NRT) analysis methods provide both optimized Lewis-structural bonding descriptors for ground-state electronic properties as well as suitable building blocks for idealized “diabatic” two-state models of the associated spectroscopic excitations. Specifically, in the framework of single-determinant Hartree-Fock or density functional methods for a resonance-stabilized molecule or supramolecular complex, we employ NBO/NRT descriptors of the ground-state determinant to develop a qualitative picture of the associated charge-transfer excitation that dominates the valence region of the electronic spectrum. We illustrate the procedure for the elementary bond shifts of SN2-type halide exchange reaction as well as the more complex bond shifts in a series of conjugated cyanine dyes. In each case, we show how NBO-based descriptors of resonance-type 3-center, 4-electron (3c/4e) interactions provide simple estimates of spectroscopic excitation energy, bond orders, and other vibronic details of the excited-state PES that anticipate important features of the full multi-configuration description. The deep 3c/4e connections to measurable spectral properties also provide evidence for NBO-based estimates of ground-state donor-acceptor stabilization energies (sometimes criticized as “too large” compared to alternative analysis methods) that are also found to be of proper magnitude to provide useful estimates of excitation energies and structure-dependent spectral shifts.

scholarly journals An Analysis of Recent BLYP and PBE-Based Range-Separated Double-Hybrid Density Functional Approximations for Main-Group Thermochemistry, Kinetics and Noncovalent Interactions

2021 ◽  
Author(s):  
Asim Najibi ◽  
Marcos Casanova Paez ◽  
Lars Goerigk
Keyword(s):  
Ground State ◽  
Density Functional ◽  
Noncovalent Interactions ◽  
Main Group ◽  
Density Functionals ◽  
Excitation Energies ◽  
Third Order ◽  
Semi Empirical ◽  
Hybrid Density Functional ◽  
Electronic Ground

<div> <div> <div> <p>We investigate the effects of range separation of the exchange energy on electronic ground-state properties for recently published double-hybrid density functionals (DHDFs) with the extensive GMTKN55 database for general main-group thermochemistry, kinetics and noncovalent interactions. We include the semi-empirical range-separated DHDFs ωB2PLYP and ωB2GP-PLYP developed by our group for excitation energies, together with their ground-state-parametrized variants, which we denote herein as ωB2PLYP18 and ωB2GP-PLYP18. We also include the non-empirical range-separated DHDFs RSX-0DH and RSX-QIDH. For all six DHDFs, damping parameters for the DFT-D3 dispersion correction (and for its DFT-D4 variant) are presented. We comment on when the range-separated functionals can be more beneficial than their global counterparts, and conclude that range separation alone is no guarantee for overall improved results. We observe that the BLYP-based functionals generally outperform the PBE-based functionals. We finally note that the best-performing double-hybrid density functionals for GMTKN55 are still the semi-empirical range-separated double hybrids ωDSD3-PBEP86-D4 and ωDSD72-PBEP86-D4, the former of which includes a third-order perturbative correlation term in addition to the more conventional second- order perturbation that DHDFs are based upon.</p> </div> </div> </div>

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.

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.

scholarly journals An Analysis of Recent BLYP and PBE-Based Range-Separated Double-Hybrid Density Functional Approximations for Main-Group Thermochemistry, Kinetics and Noncovalent Interactions

2021 ◽  
Author(s):  
Asim Najibi ◽  
Marcos Casanova Paez ◽  
Lars Goerigk
Keyword(s):  
Ground State ◽  
Density Functional ◽  
Noncovalent Interactions ◽  
Main Group ◽  
Density Functionals ◽  
Excitation Energies ◽  
Third Order ◽  
Semi Empirical ◽  
Hybrid Density Functional ◽  
Electronic Ground

<div> <div> <div> <p>We investigate the effects of range separation of the exchange energy on electronic ground-state properties for recently published double-hybrid density functionals (DHDFs) with the extensive GMTKN55 database for general main-group thermochemistry, kinetics and noncovalent interactions. We include the semi-empirical range-separated DHDFs ωB2PLYP and ωB2GP-PLYP developed by our group for excitation energies, together with their ground-state-parametrized variants, which we denote herein as ωB2PLYP18 and ωB2GP-PLYP18. We also include the non-empirical range-separated DHDFs RSX-0DH and RSX-QIDH. For all six DHDFs, damping parameters for the DFT-D3 dispersion correction (and for its DFT-D4 variant) are presented. We comment on when the range-separated functionals can be more beneficial than their global counterparts, and conclude that range separation alone is no guarantee for overall improved results. We observe that the BLYP-based functionals generally outperform the PBE-based functionals. We finally note that the best-performing double-hybrid density functionals for GMTKN55 are still the semi-empirical range-separated double hybrids ωDSD3-PBEP86-D4 and ωDSD72-PBEP86-D4, the former of which includes a third-order perturbative correlation term in addition to the more conventional second- order perturbation that DHDFs are based upon.</p> </div> </div> </div>

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.

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>

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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