Effect of electronic excitation to intermolecular proton transfer in bulk nitromethane: Tuned parameter SCC-DFTB and first principles study

2015 ◽  
Vol 14 (02) ◽  
pp. 1550013 ◽  
Author(s):  
Feng Guo ◽  
Hong Zhang ◽  
Chao-Yang Zhang ◽  
Xin-Lu Cheng ◽  
Hai-Quan Hu
Keyword(s):  
Proton Transfer ◽  
First Principles ◽  
Density Functional ◽  
Tight Binding ◽  
Transfer Reactions ◽  
Singlet Ground State ◽  
Functional Theory ◽  
Intermolecular Proton Transfer ◽  
Proton Transfer Reactions ◽  
Dynamics Simulations

To understand the reaction mechanism involving hydrogen transfers through hydrogen-bond bridge, we carried out both Self-Consistent Charge Density Functional Tight-Binding (SCC-DFTB) calculations of bulk nitromethane and Density Functional Theory (DFT) calculations of singlet ground state/triplet excited state molecular nitromethane using B3LYP functional. Firstly, we tuned the repulsive parameters of the SCC-DFTB method for nitromethane with dataset calculated from DFT at B3LYP/6-311g level. The molecular dynamics simulations are carried out with tuned parameters to get the dynamical properties of the bulk nitromethane, and the static calculations are intended to give energy profile of the reaction process. These calculations indicate the excitation of nitromethane molecule making the proton transfer reactions possible, and lowering the reaction barrier.

Potential energy construction in the diabatic picture for quantum mechanical rate constants of intermolecular proton transfer

2017 ◽  
Vol 19 (25) ◽  
pp. 16857-16866 ◽  
Author(s):  
Yuta Hori ◽  
Tomonori Ida ◽  
Motohiro Mizuno
Keyword(s):  
Proton Transfer ◽  
Rate Constants ◽  
Quantum Dynamics ◽  
Transfer Reactions ◽  
Quantum Mechanical ◽  
Simple Method ◽  
Thermal Rate Constants ◽  
Intermolecular Proton Transfer ◽  
Proton Transfer Reactions ◽  
Dynamics Simulations

We propose a simple method for potential construction in the diabatic picture and the estimation of thermal rate constants for intermolecular proton transfer reactions using quantum dynamics simulations carried out on the constructed potentials.

The effect of water-mediated catalysis on the intramolecular proton-transfer reactions of the isomers of 5-chlorouracil: a theoretical study

2019 ◽  
Vol 75 (5) ◽  
pp. 554-561
Author(s):  
Jian Zhang ◽  
Xiu Li
Keyword(s):  
Proton Transfer ◽  
Density Functional ◽  
Dft Method ◽  
Intramolecular Proton Transfer ◽  
Transfer Reactions ◽  
Energy Barriers ◽  
Transfer Energy ◽  
Geometrical Structures ◽  
Proton Transfer Reactions ◽  
Mediated Catalysis

The geometrical structures and thermal energies (E), enthalpies (H) and Gibbs free energies (G) of 13 isomers of 5-chlorouracil (5ClU) in the gas and water phases were investigated using the density functional theory (DFT) method at the M06-2X/6-311++g(3df,3pd) level. The isomers of 5ClU can be microhydrated at different molecular target sites. The mono- and dihydrated forms are the most stable in both the gas and water phases, and, because of the intermolecular interactions, the hydrations lead to a degree of change in the stability trend. Two types of isomerizations were considered: the internal H—O bond rotations in which the H atom rotates 180° around the C—O bond and the intramolecular proton-transfer reactions in which an H atom is transferred between an O atom and a neighbouring N atom. The forward and backward energy barriers for isomerizations of nonhydrated 5ClU were calculated. In addition, 16 optimized transition-state structures for water-mediated catalysis on isomerizations of 5ClU were investigated. The forward and backward proton-transfer energy barriers of water-mediated catalysis on isomerizations of 5ClU were obtained. The results indicate that the catalytic effect of two H2O molecules is much greater than that of one H2O molecule in isomerizations of 5ClU.

Composition and Strain Dependence of the Piezoelectric Coefficients in Semiconductor Alloys

2007 ◽  
Vol 1017 ◽  
Author(s):  
T. Hammerschmidt ◽  
M. A. Migliorato ◽  
D. Powell ◽  
A. G. Cullis ◽  
G. P. Srivastava
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Piezoelectric Coefficient ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Semiconductor Alloys ◽  
Binding Model ◽  
Functional Theory ◽  
Photo Current ◽  
Good Agreement

AbstractWe propose a tight-binding model for the polarization that considers direct and dipole contributions and employs microscopic quantities that can be calculated by first-principles methods, e.g. by employing Density Functional Theory (DFT). Applying our model to InxGa1-xAs alloys allows us to settle discrepancies between the values of e14 as obtained from experiments and from linear interpolations between the values of InAs and GaAs. Our calculated piezoelectric coefficient is in very good agreement with photo current measurements of InAs/GaAs(111) quantum well samples.

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