Theoretical Study on Thermodynamic Properties of C1−C16 Alkanes: A 3-Parameter Least-Squared Calibration

Abstract

The hybrid density-functional theory (DFT) calculated energies of C1−C16 straight-chain alkanes were obtained based on B3LYP/6-311++G(3df,2pd) single-point energies and the related thermal corrections of B3LYP/6-31G(d,p) optimized geometries. A 3-parameter modification equation and the least-squares approach are adopted to calibrate all the molecular calculated energies to produce accurate enthalpies of formation (ΔHf) and Gibbs free energies of formation (ΔGf), respectively. This study found that all compounds had 0.04% average relative error (A.R.E.) for the atomization energies, with a mean value of absolute error (M.A.E.) of just 1.1 kJ/mol for the ΔHf and 1.9 kJ/mol for the ΔGf of formation. The ΔHf values obtained in this work are superior to the improved G3(MP2)//B3LYP calculations for the same 16 alkanes in pertinent literature.