First-principle DFT calculations for the chemisorption and reaction of CO on the stepped Fe(310) surface were performed. It is found that among the many possible adsorption sites CO is bound preferably to the hollow sites of the (100) terraces in a tilted geometry analogous to the adsorption of CO on the regular Fe(100) surface. The computed binding energy of 42.7 kcal/mol is similar to that for the CO adsorption on a more organized Fe(100) surface. An intriguing positive correlation of the CO adsorption energy with the surface coverage is noticed; the CO binding energy is increased to 44.2 kcal/mol when the surface coverage reaches 0.500 ML. Two CO decomposition pathways on Fe(310) have been explored. These processes do not show any significant contributions to the overall rate of CO dissociation at 0.250 ML because of their low exothermicity. Nevertheless, they become very prominent at 0.500 ML; it is estimated that the presence of 30% (by surface units) Fe(310) steps on the Fe(100) surface causes a 20% increase in the decomposition of adsorbed CO at 473 K.

The synthesis, characterization, absorption, and emission spectra of MoSe2 and WSe2 nanoclusters are reported. These nanoclusters are about 3.5−6 nm (MoSe2, see graphic) and 4−7 nm (WSe2) in diameter, as measured by TEM imaging. The particles are strongly quantum confined and highly anisotropic. Electron diffraction results indicate that they are three-atoms thick, consisting of a single two-dimensional Se−Mo−Se or Se−W−Se trilayer.

Studies of the dissociative adsorption of H2 and surface diffusion of H atoms on FeCo(110) using periodic density functional theory and a slab model are reported. It is found that the bcc Fe−Co alloy in B2 phase favors the exposure of (110) plane under cleavage. The H2 molecule is adsorbed on FeCo(110) via the dissociative mechanism where H−H bond scission over an OT-Co site kinetically is the most feasible, possessing an energy barrier of merely 1.5 kcal/mol, much lower than that for the corresponding H2 adsorption on Fe(100) and Fe(110). Upon adsorption, H atoms prefer the TF-Co and TF-Fe sites so that the highest degree of coordination with the surface atoms can be achieved. The calculations reveal that H atoms may diffuse easily over the FeCo(110) surface; the rate-determining step is the migration across a SB site which requires that an activation barrier of about 4.2 kcal/mol be overcome. It is noticed that the diffusive motion TF-Fe → TF-Fe is dominant at room temperature, while at higher temperatures the diffusion TF-Fe → TF-Co prevails.

The results from a density functional theory study on the structure and reactivity of CO adsorbed on the face-centered FeCo(110) surface were reported. It is found that CO adsorbs preferentially on the on-top (OT)-Co and long-bridge (LB)-Co sites with the computed binding energies ranging from 43 to 33 kcal/mol for 0.125 and 0.500 ML, respectively. The strong Co-CO bond is attributed to the alloy formation between Fe and Co that alters the local electronic structure of surface Co atoms. Several CO decomposition paths have been explored, and all paths are found to be endothermic, as in the cases of Fe(110) and Co(0001). The path that leads to scission of CO at the LB-Co site with formation of C and O adatoms coadsorbed at LB-Co and transcription factor (TF)-Co sites, respectively, is kinetically the most feasible (E f ) 45.4 kcal/mol) and least endothermic (∆E ) 10.6 kcal/mol). High reaction temperatures are thus necessary to facilitate the CO dissociation on FeCo(110).