Recently, with the development of calculators and numerical tools, quantum computations to explore the electronic, structural and dynamic properties of matter without resorting to experimental knowledge have seen increasing development. Thus, it is possible to perform ab-initio calculations with increasing precision and for increasingly larger systems. In the scientific literature, papers using ab-initio quantum computation for the prediction of formation enthalpies is more and more numerous. The aim of this paper is to develop a theoretical method to calculate standard enthalpy of formation in gas stat for organic compounds using group contribution technics (third-order group contribution method). For the establishment of this method, 750 molecules are used. In parallel with group contribution methods, this paper presents another approach to calculate gas-state formation enthalpies based on DFT method. The calculation involved 30 molecules with at least one ring from C3 to C13. Finally, DFT and group contribution results are compared.
In this work, an artificial neural network-group contribution model is developed to predict the standard enthalpy of formation in the solid (crystal) state of pure compounds. Several classes of hydrocarbon compounds CH, oxygenated compounds CHO, nitrogen compounds CHN, and energetic compounds CHNO are investigated to propose a comprehensive and predictive model. The new model is developed and tested for 1222 organic compounds containing complex molecular structures. The performance of the new model has been compared with previous work and is shown to be far more accurate. The obtained results show an average absolute deviation of 9.33 kJ·mol −1 and a coefficient of determination of 0.9972 for the experimental values.
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