Water Clusters in an Argon Matrix: Infrared Spectra from Molecular Dynamics Simulations with a Self-Consistent Charge Density Functional-Based Tight Binding/Force-Field Potential

2015 ◽  
Vol 119 (11) ◽  
pp. 2449-2467 ◽  
Author(s):  
Aude Simon ◽  
Christophe Iftner ◽  
Joëlle Mascetti ◽  
Fernand Spiegelman
Keyword(s):  
Molecular Dynamics ◽  
Infrared Spectra ◽  
Density Functional ◽  
Water Clusters ◽  
Tight Binding ◽  
Field Potential ◽  
Argon Matrix ◽  
Binding Force ◽  
Self Consistent ◽  
Dynamics Simulations

Impact of vibronic coupling effects on light-driven charge transfer in pyrene-functionalized middle and large-sized Metalloid Gold Nanoclusters from Ehrenfest dynamics.

2021 ◽  
Author(s):  
Adrian Dominguez-Castro ◽  
Thomas Frauenheim
Keyword(s):  
Molecular Dynamics ◽  
Charge Transfer ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Gold Nanoclusters ◽  
Tight Binding ◽  
Time Dependent ◽  
Effective Strategy ◽  
Dynamics Simulations ◽  
Dependent Density

Theoretical calculations are an effective strategy to comple- ment and understand experimental results in atomistic detail. Ehrenfest molecular dynamics simulations based on the real-time time-dependent density functional tight-binding (RT-TDDFTB) approach...

Mechanisms and kinetics of initial pyrolysis and combustion reactions of 1,1-diamino-2,2-dinitroethylene from density functional tight-binding molecular dynamics simulations

2019 ◽  
Vol 97 (11) ◽  
pp. 795-804 ◽  
Author(s):  
Dong Xiang ◽  
Weihua Zhu
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Density Functional ◽  
Tight Binding ◽  
Combustion Process ◽  
Exponential Factor ◽  
Three Stages ◽  
Dynamics Simulations ◽  
Combustion Processes ◽  
Kinetics Of

The density functional tight-binding molecular dynamics approach was used to study the mechanisms and kinetics of initial pyrolysis and combustion reactions of isolated and multi-molecular FOX-7. Based on the thermal cleavage of bridge bonds, the pyrolysis process of FOX-7 can be divided into three stages. However, the combustion process can be divided into five decomposition stages, which is much more complex than the pyrolysis reactions. The vibrations in the mean temperature contain nodes signifying the formation of new products and thereby the transitions between the various stages in the pyrolysis and combustion processes. Activation energy and pre-exponential factor for the pyrolysis and combustion reactions of FOX-7 were obtained from the kinetic analysis. It is found that the activation energy of its pyrolysis and combustion reactions are very low, making both take place fast. Our simulations provide the first atomic-level look at the full dynamics of the complicated pyrolysis and combustion process of FOX-7.

scholarly journals Multiscale QM/MM Molecular Dynamics Simulations of the Trimeric Major Light-Harvesting Complex II

2021 ◽  
Author(s):  
Sayan Maity ◽  
Vangelis Daskalakis ◽  
Marcus Elstner ◽  
Ulrich Kleinekathöfer
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Chlorophyll A ◽  
Density Functional ◽  
Light Harvesting ◽  
Higher Plants ◽  
Tight Binding ◽  
Spectral Densities ◽  
Light Harvesting Complex ◽  
Dynamics Simulations

Photosynthetic processes are driven by sunlight. Too little of it and the photosynthetic machinery cannot produce the reductive power to drive the anabolic pathways. Too much sunlight and the machinery can get damaged. In higher plants, the major Light Harvesting Complex (LHCII) efficiently absorbs the light energy, but can also dissipate it when in excess (quenching). In order to study the dynamics related to the quenching process but also the exciton dynamics in general, one needs to accurately determine the so-called spectral density which describes the coupling between the relevant pigment modes and the environmental degrees of freedom. To this end, Born–Oppenheimer molecular dynamics simulations in a quantum mechanics/molecular mechanics (QM/MM) fashion utilizing the density functional based tight binding (DFTB) method have been performed for the ground state dynamics. Subsequently, the time-dependent extension of the long-range-corrected DFTB scheme has been employed for the excited state calculations of the individual chlorophyll-a molecules in the LHCII complex. The analysis of this data resulted in spectral densities showing an astonishing agreement with the experimental counterpart in this rather large system. This consistency with an experimental observable also supports the accuracy, robustness, and reliability of the present multi-scale scheme. In addition, the resulting spectral densities and site energies were used to determine the exciton transfer rate within a special pigment pair consisting of a chlorophyll-a and a carotenoid molecule which is assumed to play a role in the balance between the light harvesting and quenching modes.

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.

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