Abstract

Density functional theory calculations (DFT) were performed to investigate the Fe-facet effect on the CO₂ potential barrier as well as trajectory of CO₂ adsorption. It was found that potential barrier of CO₂ adsorption on Fe (111) is almost absent (~0.01 eV). At the same time, potential barriers of CO₂ adsorption on Fe (100) and Fe (110) are 0.10 and 0.26 eV, correspondingly. The most stable configuration of CO₂ adsorption on different Fe facets under consideration is CO₂ adsorbed on Fe (111) with heat effect –1.16 eV, whereas adsorption energies of CO₂ on Fe (100) and Fe (110) are –0.87 and –0.15 eV, correspondingly. Found values are in good agreement with literature data. Most energetically favorable trajectory of the CO₂ adsorption passes through 2-fold adsorption site (located near two neighbor Fe atoms) in case of flat Fe facets (100) and (110). Unexpectable tend to spontaneous dissociation of CO₂ molecule on desorption stage was found at distance ~2.66 Å above Fe (100) surface. Analysis of electron spin distributions allows one to conclude that dissociation is caused by excitation of CO₂ molecule accompanied with rearrangement of the spin density of the both CO₂ molecule and surface Fe (100) atoms rather than charge transfer. CO₂ dissociation on adsorption stage on Fe (100) facet was not found as well as it was not observed over other Fe facets both on desorption and on adsorption stages.