3.1 External validation
External validation could well reflect the predictive performance of ACGC model. Figure 3 expressed the scatter diagram of experimental and calculated values for the training set and the testing set. As was shown in Figure 3, most data points are closely distributed along the diagonal. The data points were well fitted both for the training set and the testing set for the model. In addition, theR 2training and R 2test values were 0.9891 and 0.9898 for Tc , 0.9887 and 0.9886 for Pc , 0.9983 and 0.9983 forVc , respectively. The small difference between these two metrics clearly demonstrates the reliability of the current model. The high correlation coefficient of the testing set demonstrated the good prediction ability of the present models.