Extended Data Fig. 3: Resolving the chemisorbed state of CO₂ on MgO(001).

Adsorption enthalpy H_ads calculated with the autoSKZCAM framework and 6 different density functional approximations for the physisorbed (orange) and chemisorbed (purple) state of CO₂ on MgO(001). These are compared against TPD measurements by Meixner et al.¹³ and Chakradhar and Burghaus¹⁴, which propose a physisorbed and chemisorbed state, respectively. The experimental errors on H_ads for this system is based on temperature programmed desorption analysis by Campbell and Sellers²³, taken as twice the standard deviation in the predicted pre-exponential factor against a test set of ~ 20 adsorbed molecules (Supplementary Section 11). The autoSKZCAM simulation errors are the root squared sum of several contributions described in Supplementary Section 9, with the majority arising from errors using a geometry optimised by density functional theory, which we estimate as twice the root-mean-squared-error from an ensemble of 6 density functional approximations.