Force field validation as N2 and ETH in all-silica CHA. As Figure shows, agreement between simulation and experiment is good to excellent for 9 out of 10 datapoints, with the outlier being ETH@FAU (grey box). In this case, the calculated heats of ethene adsorption are about 30% lower than the experimental value. A potential origin of this discrepancy may be the use of a FAU-type sample dealuminated under harsh conditions in the experimental study, which is likely to contain a rather large amount of defects that might act as preferential adsorption sites for ETH. Since agreement between experiment and simulation is considerably better for all other cases, it seems reasonable to discard this datapoint. A calculation of the overall error for PCFF, using the remaining datapoints, delivers a mean of signed errors (MSE) of -1.9 kJ/mol and a mean of unsigned errors (MUE) of 2.0 kJ/mol. For PCFF/Emami, the MSE amounts to 0.0 kJ/mol and the MUE to 1.4 kJ/mol. Although the difference in MUE is not large, the MSE is significantly reduced when using PCFF/Emami parameters, indicating that, unlike for PCFF, there is no systematic underestimation of the heats of adsorption. In the view of the very good agreement, all calculations reported in the following used PCFF parameters for ethene and chlorinated ethenes, COMPASS parameters for N2, and parameters proposed by Emami et al.