The properties of the modified surface of SnO 2 (110) with benzoic acid (Y-C 6 H 4-COOH: Y is para position relative to-COOH group) derivatives were investigated using density functional theory. Zehner et al. mentioned that the modification of surface dipole moment made it possible to tune the work function of the system. The experiment of Ganzorig et al. showed that there was a linear relationship between the dipole moment of the binding molecule and the work function change of the system using the modified surface of indium-tin oxide (ITO) with some benzoic acid derivatives. To elucidate the relation between the dipole moment of the molecule and the work function change, we investigated the modified surface of SnO 2 (110) using Sn 7 O 14 cluster model which was embedded in the fixed point charges. On the modification of the surface, benzoic acid derivatives were bound to SnO 2 surface. By changing the terminal group of benzoic acid with H, Cl, F, CF 3 and CCl 3 , the work function changed and the dipole moment of the binding molecules of the modified SnO 2 (110) were evaluated. The results showed that there was a linear relationship between the dipole moment of the binding molecules and the work function changed. From this relation, the average value of the dipole moments of Sn-OOC linkage at the surface was also evaluated.

No abstract

Tin oxide is one of the popular metal oxide semiconductor used in solar cells, sensors, and catalysts. The surface modification by organic self assembled monolayer is one of the promising techniques to tune and to control the surface work function. In our study, we investigated the work function change of the SnO 2 (110) surface which was modified with various benzoic acids derivatives using density functional theory (DFT). All calculations were carried out on Quantum Espresso program. Electron correlation and exchange parts were treated by local density (LDA), generalized gradient approximation (GGA) with Hubbard U term. To improve band structure calculation we used LDA+U method. The results of the calculation with LDA method indicated that the work functions of the pure and modified surface of SnO 2 (110) with -C 6 H 4 -COOH molecule were calculated to be 7.40 eV and 6.18 eV, respectively. As the experimental value of work function of SnO 2 (110) surface is about 7.74 eV, the results of the DFT calculation for pure SnO 2 (110) surface modification by benzoic acid derivatives are in good agreement with the experimental.

No abstract

We have investigated crystal structure of cellulose triacetate I (CTA I) by using first principal density functional theory (DFT) calculation. The results are in good agreement with the experimentally obtained crystal structure when we used the cutoff energy higher than 70 Ry. However, the cell parameters calculated without dispersion correction are overestimated the results compared to the experimental value. Contrary, with the inclusion of dispersion correction, the cell parameters were calculated slightly smaller than the experimental one. The smaller cell parameter can be considered to be reasonable because the effect of the thermal expansion is not included in the density functional calculation. That is, inclusion of the dispersion term is important in the calculation of this crystal structure of CTA I.