scholarly journals Performances of Density Functional Tight-Binding Methods for Describing Ground and Excited State Geometries of Organic Molecules

2019 ◽  
Vol 15 (11) ◽  
pp. 6267-6276 ◽  
Author(s):  
Arnaud Fihey ◽  
Denis Jacquemin
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Organic Molecules ◽  
Tight Binding

MODELING VIBRATIONAL SPECTRA USING THE SELF-CONSISTENT CHARGE DENSITY-FUNCTIONAL TIGHT-BINDING METHOD II: INFRARED SPECTRA

2005 ◽  
Vol 04 (spec01) ◽  
pp. 639-655 ◽  
Author(s):  
HENRYK A. WITEK ◽  
KEIJI MOROKUMA ◽  
ANNA STRADOMSKA
Keyword(s):  
Charge Density ◽  
Infrared Spectra ◽  
Density Functional ◽  
Organic Molecules ◽  
Tight Binding ◽  
Additional Term ◽  
Functional Theory ◽  
Molecular Electron ◽  
Self Consistent ◽  
Energy Formula

We present an extended self-consistent charge density-functional tight-binding (SCC-DFTB) method that allows for computing vibrational infrared spectra. The extension is based on introducing an additional term in the SCC-DFTB energy formula that describes effectively the interaction of external electric field with molecular electron density distribution. The extended SCC-DFTB method is employed to model vibrational infrared spectra of 16 organic molecules. The calculated spectra are compared to experiment and to spectra obtained with density functional theory. For most of the molecules, the SCC-DFTB method reproduces the experimental spectra in a very satisfactory manner. We discuss the drawbacks and possible applications of this new scheme.

scholarly journals Time-Dependent Long-Range Corrected Density-Functional Tight-Binding Method Combined with the Polarizable Continuum Model

2019 ◽  
Author(s):  
Yoshio Nishimoto
Keyword(s):  
Excited State ◽  
Long Range ◽  
Continuum Model ◽  
Density Functional ◽  
Tight Binding ◽  
Polarizable Continuum Model ◽  
Time Dependent ◽  
Dual Emission ◽  
Tight Binding Method ◽  
Polarizable Continuum

In this study, excited-state free energies and geometries were efficiently evaluated using a linear-response time-dependent long-range corrected density-functional tight-binding method integrated with the polarizable continuum model (TD-LC-DFTB/PCM). Although the LC-DFTB method required the evaluation of the exchange-type term, which was moderately computationally expensive, a single evaluation of the excited-state gradient for a system consisting of more than 1000 atoms in a vacuum was completed within 30 minutes using one CPU core. Benchmark calculations were conducted for 3-hydroxy avone, which exhibits dual emission: the absorption and enol-form emission wavelengths calculated by TD-LC-DFTB/PCM agreed well with those predicted based on density functional theory using a long-range corrected functional; however, there was a large error in the predicted keto-form emission wavelength. Further benchmark calculations for more than 20 molecules indicated that the conventional TD-DFTB method underestimated the absorption and 0-0 transition energies compared with those which were measured experimentally while the TD-LC-DFTB method systematically overestimated these metrics. Nevertheless, the agreement of the results of the TD-LC-DFTB method with those obtained by the CAM-B3LYP method demonstrates the potential of the TD-LC-DFTB/PCM method. Moreover, changing the range-separation parameter to 0.15 minimized this deviation.<br>

scholarly journals Time-Dependent Long-Range Corrected Density-Functional Tight-Binding Method Combined with the Polarizable Continuum Model

2019 ◽  
Author(s):  
Yoshio Nishimoto
Keyword(s):  
Excited State ◽  
Long Range ◽  
Continuum Model ◽  
Density Functional ◽  
Tight Binding ◽  
Polarizable Continuum Model ◽  
Time Dependent ◽  
Dual Emission ◽  
Tight Binding Method ◽  
Polarizable Continuum

In this study, excited-state free energies and geometries were efficiently evaluated using a linear-response time-dependent long-range corrected density-functional tight-binding method integrated with the polarizable continuum model (TD-LC-DFTB/PCM). Although the LC-DFTB method required the evaluation of the exchange-type term, which was moderately computationally expensive, a single evaluation of the excited-state gradient for a system consisting of more than 1000 atoms in a vacuum was completed within 30 minutes using one CPU core. Benchmark calculations were conducted for 3-hydroxy avone, which exhibits dual emission: the absorption and enol-form emission wavelengths calculated by TD-LC-DFTB/PCM agreed well with those predicted based on density functional theory using a long-range corrected functional; however, there was a large error in the predicted keto-form emission wavelength. Further benchmark calculations for more than 20 molecules indicated that the conventional TD-DFTB method underestimated the absorption and 0-0 transition energies compared with those which were measured experimentally while the TD-LC-DFTB method systematically overestimated these metrics. Nevertheless, the agreement of the results of the TD-LC-DFTB method with those obtained by the CAM-B3LYP method demonstrates the potential of the TD-LC-DFTB/PCM method. Moreover, changing the range-separation parameter to 0.15 minimized this deviation.<br>

scholarly journals Virtual Excited State Reference for the Discovery of Electronic Materials Database (VERDE Materials DB): An Open-Access Resource for Ground and Excited State Properties of Organic Molecules

2019 ◽  
Author(s):  
Biruk Abreha ◽  
Snigdha Agarwal ◽  
Ian Foster ◽  
Ben Blaiszik ◽  
Steven Lopez
Keyword(s):  
Excited State ◽  
Open Access ◽  
Organic Solar Cells ◽  
Density Functional ◽  
Organic Molecules ◽  
Electronic Materials ◽  
Photophysical Properties ◽  
Functional Theory ◽  
State Reference ◽  
Open Access Resource

<b>VERDE materials DB </b>is open-access and searchable via http://www.verdedb.org. It is focused on light-responsive π-conjugated organic molecules with applications in green chemistry, organic solar cells, and organic redox flow batteries. It includes results of our active and past virtual screening studies; to date, more than 11,000 density functional theory (DFT) calculations have been performed on at least 1,282 molecules to obtain ground- and excited-state structures and photophysical properties.

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