• Bulletin of the Korean Chemical Society
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• 제12권1호
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• pp.22-26
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• 1991

Potential energy surfaces for the proton transfer in a formamide dimer have been obtained by ab initio SCF calculations with STO-3G, 3-21G, and 4-31G basis sets and several features have been discussed. Energy minima for a formamide dimer and its tautomer are varied with basis sets. But the general features of the potential energy surfaces are similar among them.

• Bulletin of the Korean Chemical Society
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• 제21권7호
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• pp.727-733
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• 2000

Analytical potential energy surfaces have been constructed for the four-center elimination of HCI from 1,1-dichloroethylene.The potential functions are Morse-type functions which are modified by appropriate switching and attenuating functions with adjustable parameters. The parameters have been found by fitting the calculated vibrational frequencies, reaction endothermicity, equlibrium geometries of the reactant and products to those of experiments and ab initio calculations. The translational energy release obtained from classical trajectory calculations on this surface is in good agreement with the experiment.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.365-371
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• 2010

The multiconfiguration molecular mechanics (MCMM) algorithm was used to generate potential and vibrationally adiabatic energy surfaces for excited-state tautomerization in the 1:1 7-azaindole:$H_2O$ complex. Electronic structures and energies for reactant, product, transition state were computed at the CIS/6-31G(d,p) level of theory. The potential and vibrationally adiabatic energies along the reaction coordinate were generated step by step by using 16 high-level Shepard points, which were computed at the CIS/6-31G(d,p) level. This study shows that the MCMM method was applied successfully to make quite reasonable potential and adiabatic energy curves for the excited-state double proton transfer reaction. No stable intermediates are present in the potential energy curve along the reaction coordinate of the excited-state double proton transfer in the 1:1 7-azaindole:$H_2O$ complex, indicating that these two protons are transferred concertedly. The change in the bond distances along the reaction coordinate shows that two protons move very asynchronously to make an $H_3O^+$-like moiety at the transition state.

• Bulletin of the Korean Chemical Society
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• 제30권3호
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• pp.567-572
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• 2009

In this study, the effects of counter ion valency of the electrolyte on the colloidal repulsion between two parallel cylindrical particles were investigated. Electrostatic interactions of the cylindrical particles were calculated with the variation of counter ion valency. To calculate the electrical repulsive energy working between these two cylindrical particles, Derjaguin approximation was applied. The electrostatic potential profiles were obtained numerically by solving nonlinear Poission-Boltzmann (P-B) equation and calculating middle point potential and repulsive energy working between interacting surfaces. The electrical potential and repulsive energy were influenced by counter ion valency, Debye length, and surface potential. The potential profile and middle point potential decayed with the counter ion valency due to the promoted shielding of electrical charge. On the while, the repulsive energy increased with the counter ion valency at a short separation distance. These behaviors of electrostatic interaction agreed with previous results on planar or spherical surfaces.

• Bulletin of the Korean Chemical Society
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• 제29권6호
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• pp.1131-1136
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• 2008

The electrical repulsive energy between two model cylinders was calculated by solving nonlinear Poission- Boltzmann (P-B) equation under Derjaguin approximation. Effects of the surface potential, Debye screening length, and configuration of cylinders on the repulsive interaction energy were examined. Due to the anisotropy of the shape of cylinder, the interaction repulsive energy showed dependence to the configuration of particles; cylinders aligned in end-to-end configuration showed largest repulsive energy and crossed particles had lowest interaction energy. The configuration effect is originated from the curvature effect of the interacting surfaces. The curved surfaces showed less repulsive energy than flat surfaces at the same interacting surface area. The configuration dependency of interaction energy agreed with the previous analytical solution obtained under the linearized P-B equation. The approach and results present in this report would be applicable in predicting colloidal behavior of cylindrical particles.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3618-3624
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• 2012

Photodissociation dynamics of propiolic acid ($HC{\equiv}C-COOH$) at 212 nm in the gas phase was investigated by measuring rotationally resolved laser-induced fluorescence spectra of OH ($^2{\Pi}$) radicals exclusively produced in the ground electronic state. From the spectra, internal energies of OH and total translational energy of products were determined. The electronic transition at 212 nm responsible for OH dissociation was assigned as the ${\pi}_{C{\equiv}C}{\rightarrow}{\pi}^*{_{C=O}}$ transition by time-dependent density functional theory calculations. Potential energy surfaces of both the ground and electronically excited states were obtained employing quantum chemical calculations. It was suggested that the dissociation of OH from propiolic acid excited at 212 nm should take place along the $S_1/T_1$ potential energy surfaces after internal conversion and/or intersystem crossing from the initially populated $S_2$ state based upon the potential energy calculations and model calculations for energy partitioning of the available energy among products.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.2855-2860
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• 2012

The coating N-acetyl cysteine (NAC) on gold surfaces may be used to design the distribution of either gold particle adsorbed to the $ZrO_2$ surface or vice versa by adjusting the electrostatic interactions. In this study, it was performed to find out electrostatic properties of the NAC-coated-gold surface and the $ZrO_2$ surface. The surface forces between the surfaces were measured as a function of the salt concentration and pH value using the AFM. By applying the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to the surface forces, the surface potential and charge density of the surfaces were quantitatively acquired for each salt concentration and each pH value. The dependence of the potential and charge density on the concentration was explained with the law of mass action, and the pH dependence was with the ionizable groups on the surface.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.712-716
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• 2003

The semi-diabatic potential energy surfaces (PESs) of the excited states of polyatomic molecules can be constructed for use in ab initio molecular dynamics (AIMD) studies by relying on the continuity of the electronic energy, oscillator strength, and spherical extent of an excited state along with first derivatives of these quantities as computed by using the equation-of-motion coupled-cluster (EOM-CC) method. The semidiabatic PESs of both the π → $π^*$ valence excited state and the 3s-type Rydberg state of ethylene are presented and discussed in this paper, in conjunction with some of the AIMD results we obtained for these states.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.985-993
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• 1998

The second order effective valence shell Hamiltonian ($H^v$), which is based on quasidegencrate many-body perturbation theory, is applied to determining the potential energy surfaces and the dipole moment functions of the various valence states of $NH_2$. The $H^v$ calculated values are found to be in good agreement with those of other ab initio calculations or experiments. It signifies the fact that the $H^v$ is a good ab initio method to describe the energies and properties of various valence states with a same chemical accuracy. Furthermore, it is shown that the lowest (second order for energy and the first order for property) order $H^v$ method is very accurate for small molecules like $NH_2$ and the matrix elements of Hv which are computed only once are all we need to accurately describe all the valence states simultaneously.

• Bulletin of the Korean Chemical Society
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• 제25권11호
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• pp.1645-1647
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• 2004

Potential energy surfaces for the reaction Al + $O_2{\to}$AlO + O have been calculated with the multireference configuration interaction (MRCI) method using molecular orbitals derived from the complete active space selfconsistent field (CASSCF) calculations. The end-on geometry is the most favourable for the reaction to take place. The small reaction barrier in the present calculation (0.11 eV) is probably an artefact related to the ionicneutral avoided crossing. The charge analysis implies that the title oxidation reaction occurs through a harpooning mechanism. Along the potential energy surface of the reaction, there are two stable intermediates of $AlO_2(C_{{\infty}v}$ and $C_{2v}$) at least 2.74 eV below the energy of reactants. The calculated enthalpy of the reaction (-0.07 eV) is in excellent agreement with the experimental value (-0.155 eV) in part due to the fortuitous cancellation of errors in AlO and $O_2$ calculations.