We applied periodic density-functional theory to investigate the adsorption of C2H2 on the Cu/Pt bimetallic and monometallic surfaces, including Cu-Pt-Pt and Pt--Cu-Pt representing the monolayer Cu on the Pt surface and subsurface Cu in the Pt surface, respectively. For the Pt（111） and Pt-Cu-Pt surfaces, C2H2 is preferentially a 3-fold “parallel-bridge” configuration, and a ＂p-bridge＂ structure exists above the Cu（111） and Cu-Pt-Pt surfaces. The adsorption energy of C2H2 on these surfaces decreases in the order Pt（111） 〉 Cu-Pt-Pt 〉 Pt-Cu-Pt 〉 Cu（11）. The analysis of density of states, charge, and vibrational frequencies showed obviously weakening of the adsorbed C-C bond and high sp2 character on the carbon atom. Furthermore, when the top-layer compositions are equal, the nearer the EF d-band center is, the larger the C2H2 adsorption energy will be.
Density functional theory （DFT） calculations are employed to investigate the structural and electronic properties of MoS6^- and MoS6 clusters. Generalized Koopmans＇ theorem is applied to predict the vertical detachment energies and simulate the photoelectron spectra （PES）. Intriguingly, the terminal S2-, polysulfide S2^2- and S3^2- ligands simultaneously emerge in the lowest-energy structure of MoS6. Molecular orbital analyses are performed to analyze the chemical bonding in MoS6^-/0 clusters and elucidate their structural and electronic properties.
Density functional theory calculations have been performed to study the interaction of small silver clusters, Ag2-Ag9, with HCN. The adsorption of HCN on-top site of the silver cluster, among various possible sites, is energetically preferred. The adsorption energies of HCN on the silver clusters reach a local maximum at n = 4, which is only about 0.450 eV, indicating that the adsorbed HCN molecule is weakly perturbed. The adsorbed C-N and C-H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.
Carbon dioxide adsorbed on different kinds of CaO surfaces has been investigated with the help of the first principle density functional theory plane wave calculations. Various possible configurations have been considered and the calculated results showed that CO2 was strongly adsorbed by C atom bonded with the CaO （001） and （110） surfaces with adsorption energies of 1.38 and 3.22 eV, respectively. The adsorption of CO2 molecule on defect surfaces is complicated compared with that on the pristine surfaces. The adsorption energy of CO2 absorbed on the CaO（110） surface is larger than that of CaO（001） surface when the type of defect surface is the same.
The electronic and structural properties of ReO5 and ReO5 clusters are investigated using density functional theory （DFT） calculations. The lowest energy structures for both the anionic and neutral clusters are determined, and the corresponding photoelectron spectrum is simulated. Our results show that ReO5 can be described as an unusual peroxo molecule, Re（O）3（η2-O2） , while ReO5 is found to be exhibiting the O2 o radical character. Molecular orbital analyses and spin density analyses are performed to elucidate the chemical bonding and the electronic and structural properties in these two rhenium oxide clusters.
