Anharmonic Correction to Adsorption Free Energy from DFT-Based MD Using Thermodynamic Integration

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Adsorption processes often involve weak interactions where harmonic approximations for entropy are inaccurate.
• Anharmonic corrections are crucial for precise thermodynamic predictions in chemical systems.

Purpose of the Study:

• To develop and implement a robust computational method for calculating anharmonic entropy contributions in periodic systems.
• To enhance the accuracy of thermodynamic calculations for adsorption processes in computational catalysis.

Main Methods:

• Combining thermodynamic integration (TI) with curvilinear internal coordinates for periodic systems.
• Utilizing ab initio molecular dynamics within the VASP framework.
• Implementing a reaction path-independent formalism for broad applicability.

Main Results:

• Demonstrated the method's accuracy on model systems with known solutions.
• Quantified the impact of anharmonic vibrations, hindered rotations, and translations on adsorption thermodynamics.
• Successfully applied the method to study small adsorbate adsorption in H-SSZ-13 zeolite.

Conclusions:

• The developed method provides a reliable tool for accurate entropy calculations in adsorption and catalysis.
• Anharmonic effects are significant and must be considered for precise thermodynamic predictions.
• This approach advances computational studies in heterogeneous catalysis and materials science.