Self-Consistent Component Increment Theory for Predicting Enthalpy of Formation.

Area of Science:

• Computational chemistry
• Thermochemistry

Background:

• Gas-phase enthalpy of formation (ΔH_f) is crucial for reaction thermodynamics and kinetics.
• Predicting ΔH_f for large molecules remains challenging despite advances in quantum chemistry methods.

Purpose of the Study:

• To introduce a novel component increment theory, TCIT, for predicting molecular ΔH_f.
• To evaluate TCIT's performance against established methods like Benson group increment theory (BGIT).

Main Methods:

• TCIT decomposes molecular ΔH_f into additive component contributions.
• Component contributions are derived from Gaussian-4 (G4) calculations on algorithmically generated model compounds.
• TCIT was benchmarked using the Pedley, Naylor, and Kline experimental ΔH_f dataset for noncyclic compounds.

Main Results:

• TCIT demonstrated consistently lower signed and absolute errors compared to BGIT.
• The novel TCIT method shows improved accuracy in predicting ΔH_f for noncyclic compounds.

Conclusions:

• TCIT offers a more accurate approach for predicting gas-phase enthalpy of formation in large molecules.
• Future extensions of TCIT are planned for cyclic, ionic, and radical species, addressing limitations of current methods due to data scarcity.