Theoretical study of the interaction of alkali-metal atoms with CO2

Chemical interaction and coordination modes of CO2 with alkali metals M (M=Li, Na, K) have been investigated by means of density functional theory (DFT). Both gradient-corrected Perdew–Wang–Perdew and hybrid B3LYP exchange-correlation functionals were employed. Surprisingly, the behavior of Li is different from that of Na or K. For Li–CO2 the absolute minimum corresponds to a C2v structure where the CO2 molecule is rather distorted, and two other minima were found, a linear M–O–C–O and a Cs structure where M is coordinated to C but where CO2 remains almost linear. For Na and K the bond is always weak and the binding energies lie near the limit of the interactions that can be described by means of DFT.