Variational methods for the calculation of rovibrational energy levels of small molecules

1987 ◽  
Vol 83 (9) ◽  
pp. 1663 ◽  
Author(s):  
Brian T. Sutcliffe ◽  
Jonathan Tennyson
Keyword(s):  
Variational Methods ◽  
Small Molecules ◽  
Energy Levels

Semiclassical variational calculation of energy levels of He@C70

2006 ◽  
Vol 84 (2) ◽  
pp. 145-164
Author(s):  
G R Lee-Dadswell ◽  
C G Gray
Keyword(s):  
Variational Methods ◽  
Mechanical Energy ◽  
Energy Levels ◽  
High Accuracy ◽  
Variational Calculation ◽  
Quantum Mechanical ◽  
Simplified Models ◽  
Trial Solution ◽  
Quantum Mechanical Energy ◽  
Very High

Semiclassical variational methods are used to obtain estimates of the quantum mechanical energy levels for two simplified models of the potential seen by a helium atom trapped inside a C70 cage. We find that with the use of a simple trial solution, the calculations are simple. A more complicated trial trajectory, while improving some results of the calculation, makes the calculation prohibitively difficult. We also observe that as long as the precessional frequency of the orbits is small we can obtain very high accuracy in our results. However, the inability to accurately predict precessional frequencies results in poor prediction of energy levels when the precessional frequency is large.PACS No.: 5.45.Mt

scholarly journals Recent Progress in (Photo-)-Electrochemical Conversion of CO2 With Metal Porphyrinoid-Systems

2021 ◽  
Vol 9 ◽  
Author(s):  
Dženeta Dedić ◽  
Adrian Dorniak ◽  
Uwe Rinner ◽  
Wolfgang Schöfberger
Keyword(s):  
Small Molecules ◽  
Carbon Dioxide Emissions ◽  
Energy Levels ◽  
Research Area ◽  
Environmental Crisis ◽  
Small Molecule Activation ◽  
Multi Walled Carbon Nanotubes ◽  
Key Topics ◽  
Walled Carbon Nanotubes ◽  
Current Energy

Since decades, the global community has been facing an environmental crisis, resulting in the need to switch from outdated to new, more efficient energy sources and a more effective way of tackling the rising carbon dioxide emissions. The activation of small molecules such as O2, H+, and CO2 in a cost—and energy-efficient way has become one of the key topics of catalysis research. The main issue concerning the activation of these molecules is the kinetic barrier that has to be overcome in order for the catalyzed reaction to take place. Nature has already provided many pathways in which small molecules are being activated and changed into compounds with higher energy levels. One of the most famous examples would be photosynthesis in which CO2 is transformed into glucose and O2 through sunlight, thus turning solar energy into chemical energy. For these transformations nature mostly uses enzymes that function as catalysts among which porphyrin and porphyrin-like structures can be found. Therefore, the research focus lies on the design of novel porphyrinoid systems (e.g. corroles, porphyrins and phthalocyanines) whose metal complexes can be used for the direct electrocatalytic reduction of CO2 to valuable chemicals like carbon monoxide, formate, methanol, ethanol, methane, ethylene, or acetate. For example the cobalt(III)triphenylphosphine corrole complex has been used as a catalyst for the electroreduction of CO2 to ethanol and methanol. The overall goal and emphasis of this research area is to develop a method for industrial use, raising the question of whether and how to incorporate the catalyst onto supportive materials. Graphene oxide, multi-walled carbon nanotubes, carbon black, and activated carbon, to name a few examples, have become researched options. These materials also have a beneficial effect on the catalysis through for instance preventing rival reactions such as the Hydrogen Evolution Reaction (HER) during CO2 reduction. It is very apparent that the topic of small molecule activation offers many solutions for our current energy as well as environmental crises and is becoming a thoroughly investigated research objective. This review article aims to give an overview over recently gained knowledge and should provide a glimpse into upcoming challenges relating to this subject matter.

scholarly journals Triphenylamine-Merocyanine-Based D1-A1-π-A2/A3-D2 Chromophore System: Synthesis, Optoelectronic, and Theoretical Studies

2019 ◽  
Vol 20 (7) ◽  
pp. 1621 ◽  
Author(s):  
Pedada Srinivasa Rao ◽  
Avinash L. Puyad ◽  
Sidhanath V. Bhosale ◽  
Sheshanath V. Bhosale
Keyword(s):  
Charge Transfer ◽  
Small Molecules ◽  
Intramolecular Charge Transfer ◽  
Energy Levels ◽  
Fluorescence Emission ◽  
Theoretical Studies ◽  
Computational Studies ◽  
Lumo Energy ◽  
Strong Electron ◽  
System Synthesis

donor–acceptorDonor–acceptor–π–acceptor–donor (D1-A1-π-A2/A3-D2)-type small molecules, such TPA-MC-2 and TPA-MC-3, were designed and synthesized starting from donor-substituted alkynes (TPA-MC-1) via [2 + 2] cycloaddition−retroelectrocyclization reaction with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) units, respectively. TPA-MC-2 and TPA-MC-3 chromophores differ on the A2/A3 acceptor subunit, which is 1,1,4,4-tetracyanobutadiene (TCBD) and a dicyanoquinodicyanomethane (DCQDCM), respectively. Both the derivative bearing same donors D1 (triphenylamine) and D2 (trimethylindolinm) and also same A1 (monocyano) as an acceptor, tetracyano with an aryl rings as the π-bridging moiety. The incorporation of TCNE and TCNQ as strong electron withdrawing units led to strong intramolecular charge-transfer (ICT) interactions, resulting in lower LUMO energy levels. Comparative UV–Vis absorption, fluorescence emission, and electrochemical and computational studies were performed to understand the effects of the TCNE and TCNQ subunits incorporated on TPA-MC-2 and TPA-MC-3, respectively.

scholarly journals Synthesis and Optoelectronic Characterization of Perylene Diimide-Quinoline Based Small Molecules

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4406 ◽  
Author(s):  
Stefania Aivali ◽  
Loukia Tsimpouki ◽  
Charalampos Anastasopoulos ◽  
Joannis K. Kallitsis
Keyword(s):  
Small Molecules ◽  
Energy Levels ◽  
Visible Spectrum ◽  
Suzuki Coupling ◽  
Building Blocks ◽  
Fine Tuning ◽  
Perylene Diimide ◽  
Type Semiconductor ◽  
Boronic Acid Derivatives

Perylene diimide (PDI) is one of the most studied functional dyes due to their structural versatility and fine tuning of the materials properties. Core substituted PDIs are prominent n-type semiconductor materials that could be used as non-fullerene acceptors in organic photovoltaics. Herein, we develop versatile organic building blocks based on PDI by decorating the PDI core with quinoline groups. Styryl and hydroxy phenyl mono and difunctionalized molecules were prepared using mono-nitro and dibromo bay substituted PDIs by Suzuki coupling with the respective boronic acid derivatives. A novel methodology using nitro-PDI under Suzuki coupling conditions as an electrophile partner was successfully tested. Furthermore, the PDI derivatives were used for the synthesis of soluble, electron accepting small molecules combining PDI with weak electron withdrawing quinoline derivatives. The new molecules presented wide absorbance in the visible spectrum from 450 to almost 700 nm while their LUMO levels and their energy levels are in the range of −3.8 to −4.2 eV.

scholarly journals Phthalimide-based π-conjugated small molecules with tailored electronic energy levels for use as acceptors in organic solar cells

2015 ◽  
Vol 3 (34) ◽  
pp. 8904-8915 ◽  
Author(s):  
Arthur D. Hendsbee ◽  
Seth M. McAfee ◽  
Jon-Paul Sun ◽  
Theresa M. McCormick ◽  
Ian G. Hill ◽  
...  
Keyword(s):  
Solar Cells ◽  
Small Molecules ◽  
Organic Solar Cells ◽  
Energy Levels ◽  
Electronic Energy ◽  
Synthesis And Characterization ◽  
Design Synthesis ◽  
Electronic Energy Levels

The design, synthesis, and characterization of seven phthalimide-based organic π-conjugated small molecules are reported.

scholarly journals High-accuracy water potential energy surface for the calculation of infrared spectra

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170149 ◽  
Author(s):  
Irina I. Mizus ◽  
Aleksandra A. Kyuberis ◽  
Nikolai F. Zobov ◽  
Vladimir Yu. Makhnev ◽  
Oleg L. Polyansky ◽  
...  
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Small Molecules ◽  
Potential Energy Surfaces ◽  
Energy Surface ◽  
Energy Levels ◽  
High Accuracy ◽  
Wave Functions ◽  
Line Intensities ◽  
Energy Surfaces

Transition intensities for small molecules such as water and CO 2 can now be computed with such high accuracy that they are being used to systematically replace measurements in standard databases. These calculations use high-accuracy ab initio dipole moment surfaces and wave functions from spectroscopically determined potential energy surfaces (PESs). Here, an extra high-accuracy PES of the water molecule (H 2 16 O) is produced starting from an ab initio PES which is then refined to empirical rovibrational energy levels. Variational nuclear motion calculations using this PES reproduce the fitted energy levels with a standard deviation of 0.011 cm −1 , approximately three times their stated uncertainty. The use of wave functions computed with this refined PES is found to improve the predicted transition intensities for selected (problematic) transitions. A new room temperature line list for H 2 16 O is presented. It is suggested that the associated set of line intensities is the most accurate available to date for this species. This article is part of the theme issue ‘Modern theoretical chemistry’.

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