Thermochemical Properties and Quantum Mechanical Calculations

Thermochemical properties describe the energy changes and heat flows associated with chemical processes, encompassing quantities such as enthalpy, entropy and heat capacity. Accurate knowledge of these properties underpins the design of catalysts, the engineering of energy storage materials and the modelling of atmospheric and interstellar chemistries. Quantum mechanical calculations have emerged as indispensable tools for predicting thermochemical data when experimental values are unavailable or difficult to obtain. Methods range from density functional theory (DFT), which balances computational efficiency with reasonable accuracy, to high-level composite wavefunction approaches that combine multiple calculations to approach “chemical accuracy” of around ±1 kcal mol–1. Critical to these predictions are the choice of basis sets, the treatment of electron correlation and the inclusion of vibrational contributions to thermodynamic functions. Benchmarking against reliable tabulations and large data collections allows systematic quantification of uncertainties and the development of empirical corrections for temperature-dependent properties. Recent advances include automated workflows for large-scale evaluation of formation enthalpies, machine-readable datasets of gas-phase species and refined protocols for reaction equilibrium composition. Together, these developments are tightening the link between fundamental quantum theory and practical thermochemistry, enabling more predictive modelling across the chemical sciences.

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Thermochemical Properties and Quantum Mechanical Calculations publication trend

The graph below shows the total number of articles in thermochemical properties and quantum mechanical calculations across all publications each year (not limited to Nature Index journals).

Technical terms

Thermochemical properties: Quantities such as enthalpy, entropy and heat capacity that characterise heat and energy changes in chemical processes.

Enthalpy of formation: Heat change when one mole of a compound forms from its constituent elements in their reference states.

Standard entropy: Measure of molecular disorder or number of accessible states at standard conditions (298.15 K, 1 bar).

Heat capacity: Amount of heat required to raise the temperature of a substance by one degree per mole at constant pressure or volume.

Equilibrium composition: Distribution of reactants and products at chemical equilibrium under specified temperature and pressure.

Density functional theory (DFT): Quantum mechanical approach that models the electron density rather than many-electron wavefunctions to obtain electronic energies.

Composite wavefunction methods: Hierarchical quantum calculations combining different levels of theory and basis sets to approach high accuracy in thermochemical predictions.

Basis set: Mathematical functions used to represent atomic orbitals in quantum chemical calculations.

References

1. Benchmarking First-Principles Reaction Equilibrium Composition Prediction. Molecules (2023).
2. Large-scale calculations of gas phase thermochemistry: Enthalpy of formation, standard entropy, and heat capacity. The Journal of Chemical Physics (2016).
3. An Organized Collection of Theoretical Gas-Phase Geometric, Spectroscopic, and Thermochemical Data of Oxygenated Hydrocarbons, CxHyOz (x, y = 1, 2; z = 1–8), of Relevance to Atmospheric, Astrochemical, and Combustion Sciences. Journal of Physical and Chemical Reference Data (2020).
4. Uncertainty quantification in thermochemistry, benchmarking electronic structure computations, and Active Thermochemical Tables. International Journal of Quantum Chemistry (2014).