Study on the Adsorption and Activation Behaviours of Carbon Dioxide over Copper Cluster (Cu₄) and Alumina-Supported Copper Catalyst (Cu₄/Al₂O₃) by means of Density Functional Theory

Table 4

The geometrical parameters (bond lengths, d; bond angles, <) and the charges on atoms (q) for the d2 configurations and CO₂ (gas) molecule.

Parameters	CO2–Cu4 (tetrahedral) (d2b)	CO2–Cu4/Al2O3 (d2d)	CO2 (gas)
d (C–O), Å	1.279; 1.219	1.218; 1.205	1.175
<OCO, degree	134.82	157.33	180.0
d (O–Cu), Å	1.954	2.184	−
d (C–Cu), Å	1.980	2.087	−
q (CO2), e	−0.349	−0.026	−
q (Cu4), e	+0.349	+1.092	−

Note: the minimal distance from O of CO₂ to the Cu atom; the minimal distance from C of CO₂ to the Cu atom.