Calculation on the CO2 influences on the structure, stability of (MgO)m (m=1-6) clusters

The concentration of carbon dioxide (CO2) has a significant influence on the morphology of thermal decomposition products of magnesite. So, structures, stabilities and adsorption mechanisms of (MgO)(m) (m = 1-6) clusters by one or two CO2 molecules were calculated by the GGA-PW91 method. The results show that the stability of the considered clusters is (MgO)(m)(CO2)(2) clusters > (MgO)(m)(CO2) clusters > (MgO)(m) clusters by the average binding energy. Certain low-lying isomers of (MgO)(m)(CO2) and (MgO)(m)(CO2)(2) clusters which have an isolated O atom are deviating from the cluster center which possess higher kinetic activity. (MgO)(m) clusters prefer to adsorb a CO2 molecule, while (MgO)(3)(CO2) clusters prefer to adsorb a CO2 molecule rather than the neighbors. Magnesite is difficult to transit to (MgCO3)(2) clusters at room temperature. However, magnesite will spontaneously transit to (MgO)(2) clusters and further transit to MgO crystal which need to adsorb more energy at 700 K.