Why h atom prefers the on-top site and alkali metals favor the middle hollow site on the Basal plane of graphite.

In this work, the different adsorption properties of H and alkali metal atoms on the basal plane of graphite are studied and compared using a density functional method on the same model chemistry level. The results show that H prefers the "on-top site" while alkali metals favor the "middle hollow site" of graphite basal plane due to the unique electronic structures of H, alkali metals, and graphite. H has a higher electronegativity than carbon, preferring to form a covalent bond with C atoms, whereas alkaline metals have lower electronegativity, tending to adsorb on the highest electrostatic potential sites. During adsorption, there are more charges transferred from alkali metal to graphite than from H to graphite.

Partial physicochemical properties and relative stability of polyhydroxylated dibenzofurans: theoretical and experimental study.

Polyhydroxylated dibenzofuran (PHODF) is an important degradation product of polychlorinated dibenzofuran (PCDF). Four types of hydrogen bonds (the one between a hydroxyl and the oxygen atom in the matrix, between hydroxyls at ortho positions, between the oxygen atom of hydroxyl at position 1 and the hydrogen atom of the matrix at position 9, and between hydroxyls at positions 1 and 9) exist in PHODFs. The energies of the hydrogen bonds were ascertained by comparing the two configurational isomers as approximately 8-11 kJ mol⁻¹, 16-21 kJ mol⁻¹, 5-8 kJ mol⁻¹ and 23-25 kJ mol⁻¹, respectively. An experiment was designed to verify the bond energies, and the entrance geometry on main paths was studied by AIM 2000 program. The most stable in each group of configurational isomers was ascertained on the basis of evaluating the effect of hydrogen bonds. Their thermodynamic properties (standard state entropy S°, standard enthalpy Δ(f)H° and standard Gibbs energy of formation Δ(f)G°) were calculated from the combination of density functional theory (DFT) at B3LYP/6-311G** level and isodesmic reactions. Octanol/water partition coefficients (log K(ow)) were calculated on line with molinspiration methodology based on group contributions. The number and position of hydroxyl substitution (N(PHOS)) can be a good indicator of these properties for all stable PHODF congeners. The configurations most likely to form are those with a hydrogen bond (Type IV). How intramolecular hydrogen bond influences ionization was also investigated and the first-order ionization constant for each stable conformation was obtained with the self-consistent reaction field (SCRF) method.