THE LIFETIME OF CFC SUBSTITUTES STUDIED BY A NETWORK TRAINED WITH CHAOTIC MAPPING MODIFIED GENETIC ALGORITHM AND DFT CALCULATIONS

摘要

The hydrohaloalkanes have attracted much attention as potential substitutes of chlorofluorocarbons (CFCs) that deplete the ozone layer and lead to great high global warming. Having a short atmospheric lifetime is very important for the potential substitutes that may also induce ozone depiction and yield high global warming gases to be put in use. Quantitative structure-activity relationship (QSAR) studies were presented for their lifetimes aided by the quantum chemistry parameters including net charges. Mulliken overlaps, E_(HOMO) and E(LUMO) based on the density functional theory (DFT) at B3PW91 level, and the C—H bond dissociation energy based on AMI calculations. Outstanding features of the logistic mapping a simple chaotic system, especially the inherent ability to search the space of interest exhaustively have been utilized. The chaotic mapping aided genetic algorithm artificial neural network training scheme (CGANN) showed better performance than the conventional genetic algorithm ANN training when the structure of the data set was not favorable. The lifetimes of HFCs and HCs appeared to be greatly dependent on theii energies of the highest occupied molecular orbitals. The perference of the RMSRE comparing to RMSE as objective function of ANN training was better for the samples of interest with relatively short lifetimes C_2H_6 and C_3H_8 as potential green substitutes of CFCs present relatively short lifetimes.