3.5 Distinction of isomers
Figure 7 shows the error distribution of ACGC, AAG and AAGS methods. The results show that the error of ACGC is in a smaller range than that of AAG and AAGS methods for the three critical properties in Figure 7, which further demonstrates that ACF can significantly improve the calculation performance of ACGC method for the critical properties. Isomers owing to group position are analyzed in Figure 8 for critical properties, which shows that the AAE of ACGC are much smaller than these of AAG for most of isomers, especially for these with large AAE. The points in the figure are the average values of AAE obtained for molecules with the same corresponding groups. The average of AAE for all isomers of AAG model and ACGC model with critical temperature, critical pressure and critical volume are 10.2728 and 4.8844 K, 0.0809 and 0.0680 MPa, 0.0058 and 0.0040 L/kmol, respectively. After the introduction of SF and ACF, the AAE of T c,P c and V c of all isomers decreased by 52.45%, 15.95% and 31.03%, respectively. This result shows that SF and ACF can effectively distinguish isomers.