Computational analysis of vibrational frequencies and rovibrational spectroscopic constants of hydrogen sulfide dimer using MP2 and CCSD(T).

Previous studies have shown that the weakly bonded H2S dimer demands high level quantum chemical calculations to reproduce experimental values. We investigated the hydrogen bonding of H2S dimer using MP2 and CCSD(T) levels of theory in combination with aug-cc-pV(D,T,Q)Z basis sets. More precisely, the binding energies, potential energy curves, rovibrational spectroscopic constants, decomposition lifetime, and normal vibrational frequencies were calculated. In addition, we introduced the local mode analysis of Konkoli-Cremer to quantify the hydrogen bonding in the H2S dimer as well as providing for the first time the comprehensive decomposition of normal vibrational modes into local modes contributions, and a decomposition lifetime based on rate constant. The local mode force constant of the H2S dimer hydrogen bond is smaller than that of the water dimer, in accordance with the weaker hydrogen bonding in the H2S dimer.

BTEX adsorption on TiO2 anatase and rutile surfaces: DFT functionals.

Benzene, toluene, ethylbenzene, and xylenes are volatile hydrocarbons known as BTEX, which present concerns about environmental problems. Density functional theory (DFT) functionals were used for the BTEX gas phase adsorption on TiO2 (110) of rutile and (101) of anatase surfaces. Dispersion terms have shown the importance to treat weak interactions and were used to study these adsorptions using plane wave DFT calculations. All BTEX molecules have the same trend for the adsorption on rutile and anatase surfaces. The inclusion of dispersion terms has a significant contribution for the interaction energy. Density of states results suggest the hybridization between the d state of pentacoordinated titanium atoms (Ti5C) and carbon p states of benzene. The adsorption energy values indicate an effective interaction between the BTEX and surfaces, mainly due to the aromatic π interaction, which is present in all adsorbates. However, for p-xylene the methyl hydrogen directs the second major influence. Graphical abstract Charge difference showing the system with the smallest interaction and the one with the largest interaction.