• Proceedings of the Korean Vacuum Society Conference
• /
• 1996.06a
• /
• pp.123-123
• /
• 1996

• Proceedings of the Korean Magnestics Society Conference
• /
• 1996.10a
• /
• pp.42-43
• /
• 1996

• Proceedings of the Korean Magnestics Society Conference
• /
• 2004.06a
• /
• pp.30-31
• /
• 2004

• Proceedings of the Korean Magnestics Society Conference
• /
• 2012.05a
• /
• pp.14-14
• /
• 2012

• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.12a
• /
• pp.11-11
• /
• 2008

• Bulletin of the Korean Chemical Society
• /
• v.24 no.6
• /
• pp.739-743
• /
• 2003

New quaternary compounds $ANb_2PS_{10}$ (A = Na, Ag) and $AuNb_4P_2S_{20}$ were synthesized and characterized. The structures of three compounds consist of one-dimensional infinite chains built by [$Nb_2S_{12}$] and [$PS_4$] units. Cation atoms are occupied within the van der Waals gap of sulfur atoms between infinite chains to make -S…$M^+$…S- contacts. There is only one Au atom site and so crystallographically a unit cell contains four equivalent Au atoms in $AuNb_4P_2S_{20}$. This is only the half of the numbers of Na or Ag atoms in $NaNb_2PS_{10}$ or $AgNb_2PS_{10}$. The ratio between $Nb_2PS_{10}$ matrix vs the cation is, therefore, 1 : 1 for Ag and Na, but it is 2 : 1 for Au. Mixed valency in Au or Nb was expected to balance the charge in the latter compound. The electronic structures calculated based on the extended Huckel tight-binding method show that $ANb_2PS_{10}$ (A = Ag, Na) are semiconducting, while $AuNb_4P_2S_{20}$ is metallic, which is not consistent with the experimental results of these three compounds that all exhibit semiconducting property. The result of calculation suggests that $AuNb_4P_2S_{20}$ might be a magnetic insulator. Magnetic measurement experiment exactly proved that the compound is a Slater antiferromagnetic material with the Neels' temperature of 45 K. It is recognized, therefore, that electronic structure analysis is very useful to understand the properties of compounds.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.7
• /
• pp.2279-2285
• /
• 2011

The geometries, electronic structures and absorption spectra of the two organic triphenylamine-based dyes TA-St-CA and TA-DM-CA, containing identical electron donors and acceptors but the different conjugated bridges, were studied by density functional theory (DFT) at the B3LYP and PBE1PBE levels, respectively. The influence of para-orientating methoxyl units on the electronic structures and light absorption properties of the dyes and the consequent photovoltaic performance of the dye-sensitized solar cells (DSSCs) were investigated in detail. The results indicate that the introduction of the para-orientating methoxyl units into the conjugated bridge induces the increased absorption wavelength as well as the more negative EHOMO corresponding to the bigger driving force $(E_{I^-/I^-_3}-E_{HOMO})$ for dye reduction, which together improve the photovoltaic performance of TA-DM-CA, although there is a decline of the open circuit voltage caused by the more negative $E_{LUMO}$.

• Journal of the Korean Chemical Society
• /
• v.60 no.4
• /
• pp.239-244
• /
• 2016

We investigated the structures and electronic properties of Cu_mSiO_m+1 clusters with m = 0 - 7. For these clusters, we replaced a Cu atom in the copper oxide clusters with a Si atom. The B3LYP functional and LANL2DZ basis set were used for optimization of the molecular structures of all neutral and charged clusters. The bond distances, bond angles, and Mulliken charges were calculated to study the structural properties. In addition, in order to understand the electronic properties, we examined the ionization energies, electronic affinities, and second differences in energies.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2012.11a
• /
• pp.117-118
• /
• 2012

In this study, the magnetic and electronic properties of ${\alpha}-Mn$ have been investigated using the all-electron FLAPW method based on the GGA. The local magnetic moment of Mn atoms are consistent with previously calculated results. Detailed discussion on the structural, magnetic, and electronic properties of ${\alpha}-Mn$ will be given.

• Journal of the Korean Chemical Society
• /
• v.57 no.6
• /
• pp.677-683
• /
• 2013

A theoretical study of the electronic structures of $TiC_{1-x}$ and $Ti_{1-x}W_xC$ (x = 0, 0.25) is presented. The density of states and crystal orbital overlap population calculations were used to interpret variations of elastic properties induced by carbon vacancies and alloying substitutions. Our results show why the introduction of vacancies into TiC reduces bulk moduli, while W substitution at a Ti site increases the elastic modulus. The effect of the point defects on the bonding in TiC is investigated by means of extended Huckel tight-binding band calculations.