Enthalpy of formation of sodium, magnesium and lithium compounds with composite methods

Abstract

The heats of formation of forty-six molecules containing sodium, lithium and magnesium atoms have been calculated using G3X-CEP, G3X(CCSD)-CEP, G4, EnAt1, EnAt2, G3B3, G3MP2B3, CBS-QB3 and functionals using the atomization. The discrepancies between the predicted and the reported heats of formation vary in the range of 0.0–85 kcal mol⁻¹. The best agreement with experimental data was achieved by using Gn and Gn-CEP multilevel techniques. It was found that the best performance among density functional theory (DFT) methods within the atomization approach demonstrated the long range corrected LC-wPBE and BMK level theory. Composite methods presented the best results when compared with DFT. The G4, which was recently reported as a very accurate method for calculating enthalpies of formation, presented the best results when compared with DFT and other composite methods.