• Bulletin of the Korean Chemical Society
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• v.21 no.5
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• pp.510-514
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• 2000

Molecular hydrogen dimer, ($H_2)_2$ is a weakly bound van der Waals complex. The configuration of two hydrogen molecules and the potential well structure of the dimer have been the subjects of various studies among chemists and astrophysicists. In this study, we used DFT, MCG2, and MCG3 methods to determine the structure and energy of the molecular hydrogen dimer. We compared the results with previously reported ab initio method results. The ab initio results were also recalculated for comparison. All optimized geometries obtained from the MP2 and DFT methods are T-shaped. The H-H bond lengths for the dimer are almost the same as those of monomer. The center-to-center distance depeds on the levels of theory and the size of the basis sets. The bond lengths of the $H_2$ molecule from the MCG2 and MCG3 methods are shown to be in excellent agreement with the experimental value. The geometry of optimized dimer is T-shaped, and the well depths for the dimerization potential are very small, being 23 $cm-^1$ and 27 $cm-^1$ at the MCG2 and MCG3 levels, respectively. In general the MP2 level of theory predicts stronger van der Waals than the DFT, and agrees better with the MCG2 and MCG3 theories.

• Current Optics and Photonics
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• v.6 no.3
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• pp.337-343
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• 2022

Microfluidic chips are new devices that can manipulate liquids at the micrometer level, and terahertz (THz) time-domain spectroscopy has good applicability in biochemical detection. The combination of these two technologies can shorten the distance between sample and THz wave, reduce THz wave absorption by water, and more effectively analyze the kinetics of biochemical reactions in aqueous solutions. This study investigates the effects of different external magnetic field intensities on the THz transmission characteristics of deionized water, CuSO₄, CuCl₂, (CH₃COO)₂Cu, Na₂SO₄, NaCl, and CH₃COONa; the THz spectral intensity of the sample solutions decrease with increasing intensity of the applied magnetic field. Analysis shows that the magnetic field leads to a change in the dipole moment of water molecules in water and electrolyte solutions, which enhances not only the hydrogen-bond networking ability of water but also the hydration around ions in electrolyte solutions, increasing the number of hydrogen bonds. Increasing the intensity of this magnetic field further promotes the hydrogen-bond association between water molecules, weakening the THz transmission intensity of the solution.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2891-2892
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• 2011

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1321-1324
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• 2002

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.337-339
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.159-159
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• 2008

• Journal of the Korean Chemical Society
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• v.62 no.5
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• pp.412-416
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• 2018

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.889-890
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• 2003

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1202-1204
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• 2014

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.262-266
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• 1997

The CNDO/2 calculations have been applied on cluster models for the representative hydroxyls on silica surface to get Wiberg bond orders, total energies, LUMO energies, dipole moments, and formal charge densities. The Br${\ddot{o}}$nsted acidities of suggested models for the hydroxyls were explained in terms of Wiberg bond orders. The calculated bond orders of cluster models have been changed remarkably according to the hydrogen bond. However the Lewis acidities of terminal hydroxyls on silica surface were not related to the structure of hydroxyls.