• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.387-396
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• 2015

The DFT and ab initio calculations have been performed to elucidate hydrogen interaction of HOOO-(H₂O)_n (n=1~5) clusters. The optimized geometries, harmonic vibrational frequencies, and binding energies are predicted at various levels of theory. The trans conformer of HOOO monomer is predicted to be thermodynamically more stable than cis form at the CCSD(T) level of theory. For HOOO-(H₂O)_n clusters, the geometries are optimized at B3LYP/aug-cc-pVTZ and CAM-B3LYP/aug-cc-pVTZ levels of theory. The binding energy of HOOO-H₂O cluster is predicted to be 6.05 kcal/mol at the MP2//CAM-B3LYP/ aug-cc-pVTZ level of theory after zero-point vibrational energy (ZPVE) and basis set superposition error (BSSE) correction. The average binding energy per H₂O is increased according to adding a H₂O moiety in HOOO-(H₂O)_n clusters up to 7.2 kcal/mol for n=5.

• Analytical Science and Technology
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• v.20 no.1
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• pp.61-69
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• 2007

The geometrical parameters, total and relative energies, vibrational frequencies, the HOMO-LUMO energy gap, and reorganization energies for the neutral molecule, anion, and cation of $C_{16}H_{16}O_3$ have been determined using density functional method (DFT). The highest level of theory employed in this study is $B3LYP/6-311G^{**}$. Harmonic vibrational frequencies were determined at the $B3LYP/6-311G^{**}$ level of theory. All positive vibrational frequencies were obtained to confirm minimum structures. The HOMO-LUMO energy gap and reorganization energies were calculated to predict the charge transport property of liquid-crystal.

• Journal of the Korean Chemical Society
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• v.57 no.2
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• pp.216-220
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• 2013

The hydroalumination of cyclopropane has been investigated using the B3LYP density functional method employing several split-valence basis sets. It is shown that the reaction proceeds via an intermediate weakly bound complex and a four-centered transition state. Calculations at higher levels of theory were also performed at the geometries optimized at the B3LYP level, but only slight changes in the barriers were observed. Structural parameters for the transition state are also reported.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.145-151
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• 2011

ZnSe, as a II-VI compound semiconductor which has a wide band gap in the visible region is applicable to the various fields such as laser diode, display and solar cell. By using the electrochemical deposition method, ZnSe thin film was synthesized on the ITO glass substrate. The synthesis of ZnSe grains and their structure having zinc blende shape were verified through the analysis of XRD and SEM. UV spectrophotometric method determined the band gap as the value of 2.76 eV. Applying the DFT (Density Functional Theory) in the molecular dynamics, the band structure of ZnSe grains was analyzed. For ZnSe grains with zinc blende structure, the band structure and its density of state were simulated using LDA (Local Density Approximation), PBE (Perdew Burke Ernzerhof), and B3LYP (Becke, 3-parameter, Lee-Yang-Parr) functionals. Among the calculations of energy band gap upon each functional, the simulated one of 2.65 eV based on the B3LYP functional was mostly near by the experimental measurement.

• Journal of the Korean Chemical Society
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• v.48 no.3
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• pp.229-235
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• 2004

For the study of hydrogen bonding phenomenon of high energetic compounds, we have been carried out a theoretical calculations for the nitromethane with the program Gaussian-98. The calculations at levels of restricted BLYP/6-311++G(d,p), B3LYP/6-311++G(d,p) and MP2/6-311++G have been performed to obtain molecular structures, hydrogen bonding effects and vibrational spectra of nitromethane monomer and dimer. The results show nitromethane is favored to make two hydrogen bonds between molecules and the nitromethane dimer is more stable than the monomer about 15.2, 19.4 and 32.6 kJ/mol for the BLYP, B3LYP, and MP2 level calculations, respectively.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3738-3742
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• 2013

The reaction mechanism of $SiF_2$ radical with HNCO has been investigated by the B3LYP method of density functional theory(DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/$6-311++G^{**}$ level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)/$6-311++G^{**}$//B3LYP/$6-311++G^{**}$ level. $SiF_2+HNCO{\rightarrow}IM3{\rightarrow}TS5{\rightarrow}IM4{\rightarrow}TS6{\rightarrow}OSiF_2CNH(P3)$ was the main channel with low potential energy, $OSiF_2CNH$ was the main product. The analyses for the combining interaction between $SiF_2$ radical and HNCO with the atom-in-molecules theory (AIM) have been performed.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.899-904
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• 2014

The atomic structures and electronic properties of six classical and nonclassical $H_2O$@$C_{24}$ fullerene regioisomers are systematically studied using the hybrid density functional B3LYP method and M06-2X method with empirical dispersion in conjunction with the 6-31G(d,p) basis sets. The charge transfer, frontier orbitals, dipole moment, energy gap between the HOMO and LUMO, and volume change of the $C_{24}$ cage are analyzed upon encapsulation of a $H_2O$ molecule in each $C_{24}$ regioisomer. All encapsulation processes are endothermic and the relative stabilities of six $C_{24}$ fullerene regioisomers change upon encapsulation of $H_2O$.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.277-280
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• 2011

We studied the relative stability and atomic structure of five $C_{20}^{2+}$ isomers obtained by two-electron ionization of a $C_{20}$ cage (the smallest fullerene). All the isomers are bond-stretch isomers, i.e., they differ in bond length. In particular, in one of the isomers with Ih symmetry, all the bond lengths are equal. Full geometry optimizations of the dipositive ion $C_{20}^{2+}$ were performed using the hybrid density functional (B3LYP/6-31G(d)) methods. All isomers were found to be true minima by frequency analysis at the level of B3LYP/6-31G(d) under the reinforced tight convergence criterion and a pruned (99,590) grid. The zero-point correction energy for the cage bond-stretch isomers was in the increasing order $D_{2h}<C_{2h}<C_2<T_h<I_h$ of $C_{20}^{2+}$. The energy difference among the isomers of cage dipositive ions was less than that among neutral cage isomers. Our results suggest that these isomers show bond-stretch isomerism and that they have an identical spin state and an identical potential energy curve. Although the predominant electronic configurations of the isomers are similar, the frontier orbital characteristics are different, implying that we could anticipate an entirely different set of characteristic chemical reactions for each type of HOMO and LUMO.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1875-1880
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• 2010

A dicycle pyrazoline derivative, 1-phenyl-5-(p-fluorophenyl)-3,4-($\alpha$-p-fluoro-tolylenecyclohexano) pyrazoline, was synthesized and characterized by elemental analysis, IR, UV-vis, fluorescence spectra and X-ray single crystal diffraction. Density function theory (DFT) calculations were performed by using B3LYP method with 6-$311G^{**}$ basis set. The optimized geometry can well simulate the molecular structure. Vibrational frequencies were predicted, assigned and compared with the experimental values, which suggest that B3LYP/6-$311G^{**}$ method can well predict the IR spectra. Both the experimental electronic absorption spectra and the predicted ones by B3LYP/6-$311G^{**}$ method reveal three electron-transition bands, with the theoretical ones having some red shifts compared with the experimental data. Natural bond orbital analyses indicate that the absorption bands are mainly derived from the contribution of n $\rightarrow\pi^*$ and $\pi\rightarrow\pi^*$ transitions. Fluorescence spectra determination shows that the title compound can emit blue-light at about 478 nm. On the basis of vibrational analysis, the thermodynamic properties of title compound at different temperature have been calculated, revealing the correlations between $C^0_{p,m}$, $S^0_m$, $H^0_m$ and temperature.

• Journal of the Korean Chemical Society
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• v.53 no.1
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• pp.7-16
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• 2009

The global minimum structures of the benzene-water, Bz-$H_2O$ and benzene-water cation complex, [Bz-$H_2O]^+$ have been investigated using ab initio and density functional theory(DFT) with very large basis sets. The highest levels of theory employed in this study are B3LYP/cc-pVQZ for geometry optimization and MP2/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ for binding energy. The harmonic vibrational frequencies and IR intensities are also determined at the various levels of theory to confirm whether the structure of water complex is affected by the presence of benzene. The binding energies of Bz-$H_2O$ (N-1) structure are predicted to be 3.92 kcal/mol ($D_e$) and 3.11 kcal/mol ($D_0$) after the zero-point vibrational energy correction at the MP2/cc-pVQZ//B3LYP/cc-pVQZ level of theory. The binding energies of [Bz-$H_2O]^+$ (C-1) structure are predicted to be 9.06 kcal/mol for $D_e$ and 7.82 kcal/mol for $D_0$ at the same level of theory.